bibcode
stringlengths 19
19
| title
stringlengths 13
334
| abstract
stringlengths 103
2.97k
⌀ | verified_uat_ids
listlengths 1
12
| verified_uat_labels
listlengths 1
12
|
|---|---|---|---|---|
2021ApJ...908..216V
|
How to Search for Multiple Messengers—A General Framework Beyond Two Messengers
|
Quantification of the significance of a candidate multi-messenger detection of cosmic events is an emerging need in the astrophysics and astronomy communities. In this paper we show that a model-independent optimal search does not exist, and we present a general Bayesian method for the optimal model-dependent search, which is scalable to any number and any kind of messengers, and applicable to any model. In the end, we demonstrate it through an example for a joint gravitational wave, high-energy neutrino, short gamma-ray burst event search; which has not been examined heretofore.
|
[
1100,
675,
628,
1043,
739,
1912,
1882,
1885,
1887,
1900,
1886
] |
[
"neutrino astronomy",
"gravitational wave astronomy",
"gamma-ray astronomy",
"astronomical methods",
"high energy astrophysics",
"model selection",
"astrostatistics",
"astrostatistics strategies",
"astrostatistics tools",
"bayesian statistics",
"astrostatistics techniques"
] |
2024ApJ...967...93Z
|
Revisiting High-energy Polarization from Leptonic and Hadronic Blazar Scenarios
|
X-ray and MeV polarization can be powerful diagnostics for leptonic and hadronic blazar models. Previous predictions are mostly based on a one-zone framework. However, recent IXPE observations of Mrk 421 and 501 strongly favor a multizone framework. Thus, the leptonic and hadronic polarization predictions need to be revisited. Here we identify two generic radiation transfer effects, namely, double depolarization and energy stratification, that can have an impact on the leptonic and hadronic polarization. We show how they are generalized from previously known multizone effects of the primary electron synchrotron radiation. Under our generic multizone model, the leptonic polarization degree is expected to be much lower than the one-zone prediction, unlikely detectable in most cases. The hadronic polarization degree can reach a value as high as the primary electron synchrotron polarization during simultaneous multiwavelength flares, consistent with the one-zone prediction. Therefore, IXPE and future X-ray and MeV polarimeters such as eXTP, COSI, and AMEGO-X, have good chances to detect hadronic polarization during flares. However, the hadronic polarization cannot be well constrained during the quiescent state. Nonetheless, if some blazar jets possess relatively stable large-scale magnetic structures, as suggested by radio observations, a nontrivial polarization degree may show up for the hadronic model after a very long exposure time (≳1 yr).
|
[
164,
739,
1278,
1390
] |
[
"blazars",
"high energy astrophysics",
"polarimetry",
"relativistic jets"
] |
2022ApJ...939...42H
|
Axisymmetric Pulsar Magnetosphere Revisited
|
We present a global kinetic plasma simulation of an axisymmetric pulsar magnetosphere with self-consistent e <SUP>±</SUP> pair production. We use the particle-in-cell method and log-spherical coordinates with a grid size 4096 × 4096. This allows us to achieve a high voltage induced by the pulsar rotation and investigate pair creation in a young pulsar far from the death line. We find the following: (1) The energy release and e <SUP>±</SUP> creation are strongly concentrated in the thin, Y-shaped current sheet, with a peak localized in a small volume at the Y-point. (2) The Y-point is shifted inward from the light cylinder by ~15% and "breathes" with a small amplitude. (3) The dense e <SUP>±</SUP> cloud at the Y-point is in ultrarelativistic rotation, which we call superrotation, because it exceeds corotation with the star. The cloud receives angular momentum flowing from the star along the poloidal magnetic field lines. (4) Gamma-ray emission peaks at the Y-point and is collimated in the azimuthal direction, tangent to the Y-point circle. (5) The separatrix current sheet between the closed magnetosphere and the open magnetic field lines is sustained by the electron backflow from the Y-point cloud. Its thickness is self-regulated to marginal charge starvation. (6) Only a small fraction of dissipation occurs in the separatrix inward of the Y-point. A much higher power is released in the equatorial plane, including the Y-point where the created dense e <SUP>±</SUP> plasma is spun up and intermittently ejected through the nozzle between the two open magnetic fluxes.
|
[
1408,
1261,
994
] |
[
"rotation powered pulsars",
"plasma astrophysics",
"magnetic fields"
] |
2023ApJ...954..134K
|
SPYGLASS. IV. New Stellar Survey of Recent Star Formation within 1 kpc
|
Young stellar populations provide a powerful record that traces millions of years of star formation history in the solar neighborhood. Using a revised form of the SPYGLASS young star identification methodology, we produce an expanded census of nearby young stars (age < 50 Myr). We then use the HDBSCAN clustering algorithm to produce a new SPYGLASS Catalog of Young Associations, which reveals 116 young associations within 1 kpc. More than 25% of these groups are largely new discoveries, as 20 are substantively different from any previous definition, and 10 have no equivalent in the literature. The new associations reveal a yet undiscovered demographic of small associations with little connection to larger structures. Some of the groups we identify are especially unique for their high transverse velocities, which can differ from the solar velocity by 30-50 km s<SUP>-1</SUP>, and for their positions, which can reach up to 300 pc above the galactic plane. These features may suggest a unique origin, matching existing evidence of infalling gas parcels interacting with the disk interstellar medium. Our clustering also suggests links between often-separated populations, hinting to direct structural connections between Orion Complex and Perseus OB2, and between the subregions of Vela. The ~30 Myr old Cepheus-Hercules association is another emerging large-scale structure, with a size and population comparable to Sco-Cen. Cep-Her and other similarly aged structures are also found clustered along extended structures perpendicular to known spiral arm structure, suggesting that arm-aligned star formation patterns have only recently become dominant in the solar neighborhood.
|
[
1582,
1834,
1833,
1569,
1140,
1290,
1581
] |
[
"stellar associations",
"young stellar objects",
"young star clusters",
"star formation",
"ob associations",
"pre-main sequence stars",
"stellar ages"
] |
2021ApJ...919...49Z
|
SN 2017fgc: A Fast-expanding Type Ia Supernova Exploded in Massive Shell Galaxy NGC 474
|
We present extensive optical photometric and spectroscopic observations of the high-velocity (HV) Type Ia supernova (SN Ia) 2017fgc, covering the phase from ~12 days before to ~389 days after maximum brightness. SN 2017fgc is similar to normal SNe Ia, with an absolute peak magnitude of ${M}_{\max }^{B}\approx $ -19.32 ± 0.13 mag and a post-peak decline of Δm<SUB>15</SUB>(B) = 1.05 ± 0.07 mag. Its peak bolometric luminosity is derived as (1.32 ± 0.13) × 10<SUP>43</SUP> erg s<SUP>-1</SUP>, corresponding to a <SUP>56</SUP>Ni mass of 0.51 ± 0.03 M<SUB>⊙</SUB>. The light curves of SN 2017fgc are found to exhibit excess emission in the UBV bands in the early nebular phase and pronounced secondary shoulder/maximum features in the RrIi bands. Its spectral evolution is similar to that of HV SNe Ia, with a maximum-light Si II velocity of 15,000 ± 150 km s<SUP>-1</SUP> and a post-peak velocity gradient of ~120 ± 10 km s<SUP>-1</SUP> day<SUP>-1</SUP>. The Fe II and Mg II lines blended near 4300 Å and the Fe II, Si II, and Fe III lines blended near 4800 Å are obviously stronger than those of normal SNe Ia. Inspecting a large sample reveals that the strength of the two blends in the spectra, and the secondary peak in the i/r-band light curves, are found to be positively correlated with the maximum-light Si II velocity. Such correlations indicate that HV SNe Ia may experience more complete burning in the ejecta and/or that their progenitors have higher metallicity. Examining the birthplace environment of SN 2017fgc suggests that it likely arose from a stellar environment with young and high-metallicity populations.
|
[
1668,
1728
] |
[
"supernovae",
"type ia supernovae"
] |
2023ApJS..265....5H
|
A Comprehensive Study of Galaxies at z 9-16 Found in the Early JWST Data: Ultraviolet Luminosity Functions and Cosmic Star Formation History at the Pre-reionization Epoch
|
We conduct a comprehensive study on dropout galaxy candidates at z ~ 9-16 using the first 90 arcmin<SUP>2</SUP> James Webb Space Telescope (JWST) Near Infrared Camera images taken by the early release observations (ERO) and early release science programs. With the JWST simulation images, we find that a number of foreground interlopers are selected with a weak photo-z determination (Δχ <SUP>2</SUP> > 4). We thus carefully apply a secure photo-z selection criterion (Δχ <SUP>2</SUP> > 9) and conventional color criteria with confirmations of the ERO Near Infrared Spectrograph spectroscopic redshifts, and obtain a total of 23 dropout galaxies at z ~ 9-16, including two candidates at ${z}_{\mathrm{phot}}={16.25}_{-0.46}^{+0.24}$ and ${16.41}_{-0.55}^{+0.66}$ . We perform thorough comparisons of dropout galaxies found in our work with recent JWST studies, and conclude that our galaxy sample is reliable enough for statistical analyses. We derive the UV luminosity functions at z ~ 9-16, and confirm that our UV luminosity functions at z ~ 9 and 12 agree with those determined by other Hubble Space Telescope and JWST studies. The cosmic star formation rate (SFR) density decreases from z ~ 9 to 12, and perhaps to 16, but the densities at z ~ 12-16 are higher than the constant star formation efficiency model. Interestingly, there are six bright galaxy candidates at z ~ 10-16 with M <SUB>UV</SUB> < -19.5 mag and M <SUB>*</SUB> ~ 10<SUP>8-9</SUP> M <SUB>⊙</SUB>. Because a majority (~80%) of these galaxies show no signatures of active galactic nuclei in their morphologies, the high cosmic SFR densities and the existence of these UV-luminous galaxies are explained by the lack of suppression of star formation by the UV background radiation at the pre-reionization epoch and/or an efficient UV radiation production by a top-heavy initial mass function with Population III-like star formation.
|
[
594,
595,
734
] |
[
"galaxy evolution",
"galaxy formation",
"high-redshift galaxies"
] |
2022ApJ...928...41L
|
Observations of Extremely Strong Magnetic Fields in Active Region NOAA 12673 Using GST Magnetic Field Measurement
|
We present a detailed study of very strong magnetic fields in the NOAA Active Region (AR) 12673, which was the most flare productive AR in solar cycle 24. It produced four X-class flares including the X9.3 flare on 2017 September 6 and the X8.2 limb event on September 10. Our analysis is based on direct measurements of full Zeeman splitting of the Fe I 1564.85 nm line using all Stokes I, Q, U, and V profiles. This approach allowed us to obtain reliable estimates of the magnitude of magnetic fields independent of the filling factor and atmosphere models. Thus, the strongest fields up to 5.5 kG were found in a light bridge (LB) of a spot, while in the dark umbra magnetic fields did not exceed 4 kG. In the case of the LB, the magnitude of the magnetic field is not related to the underlying continuum intensity, while in the case of umbral fields we observed a well-known anticorrelation between the continuum intensity and the field magnitude. In this study, the LB was cospatial with a polarity inversion line of δ-sunspot, and we speculate that the 5.5 kG strong horizontal fields may be associated with a compact twisted flux rope at or near the photosphere. A comparison of the depth of the Zeeman π and σ components showed that in the LB magnetic fields are, on average, more horizontal than those in the dark umbra.
|
[
1979,
1503
] |
[
"delta sunspots",
"solar magnetic fields"
] |
2024ApJ...962...90D
|
Disentangling CO Chemistry in a Protoplanetary Disk Using Explanatory Machine-learning Techniques
|
Molecular abundances in protoplanetary disks are highly sensitive to the local physical conditions, including gas temperature, gas density, radiation field, and dust properties. Often multiple factors are intertwined, impacting the abundances of both simple and complex species. We present a new approach to understanding these chemical and physical interdependencies using machine learning. Specifically, we explore the case of CO modeled under the conditions of a generic disk and build an explanatory regression model to study the dependence of CO spatial density on the gas density, gas temperature, cosmic-ray ionization rate, X-ray ionization rate, and UV flux. Our findings indicate that combinations of parameters play a surprisingly powerful role in regulating CO abundance compared to any singular physical parameter. Moreover, in general we find the conditions in the disk are destructive toward CO. CO depletion is further enhanced in an increased cosmic-ray environment and in disks with higher initial C/O ratios. These dependencies uncovered by our new approach are consistent with previous studies, which are more modeling intensive and computationally expensive. Our work thus shows that machine learning can be a powerful tool not only for creating efficient predictive models, but also for enabling a deeper understanding of complex chemical processes.
|
[
1300,
75,
2237,
1914
] |
[
"protoplanetary disks",
"astrochemistry",
"chemical reaction network models",
"regression"
] |
2024AJ....167...58N
|
HybPSF: Hybrid Point-spread Function Reconstruction for the Observed JWST NIRCam Image
|
The James Webb Space Telescope (JWST) marks a new era of astronomical observation and discovery, providing unrivaled precision in various measurements, including photometry, morphology, and shear measurement. Accurate point-spread function (PSF) models are essential for many of these measurements. In this paper, we introduce HybPSF, a hybrid PSF construction method for JWST NIRCam imaging data that combines the WebbPSF software, which simulates the PSF for JWST, with observed data to produce more accurate and reliable PSF models. We apply this method to the SMACS J0723 imaging data and construct supplementary structures from residuals obtained by subtracting the WebbPSF PSF model from the data. Our results show that HybPSF significantly reduces discrepancies between the PSF model and the data compared to WebbPSF. Specifically, the PSF shape parameter ellipticity and size comparisons indicate that HybPSF improves precision by approximately 10 times for R <SUP>2</SUP> and 50% for e. This improvement has important implications for astronomical measurements using JWST NIRCam imaging data.
|
[
670,
584,
1858
] |
[
"gravitational lensing",
"galaxy clusters",
"astronomy data analysis"
] |
2023ApJ...949..121C
|
Exploring the Observability of Surviving Companions of Stripped-envelope Supernovae: A Case Study of Type Ic SN 2020oi
|
Stripped-envelope (SE) supernovae (SNe) were considered as the explosions of single massive stars with strong stellar winds, while later observations favor binary origins. One direct piece of evidence to support the binary origins is to find the surviving companions of SE SNe because previous numerical studies suggested that the binary companion should survive the SN impact and could be detectable. Recently, Gagliano et al. reported that the nearby Type Ic SN 2020oi in M100 (~17.1 Mpc) resulted from a binary system based on the Hubble Space Telescope photometric and spectroscopic observation. Based on the suggested binary properties of SN 2020oi, we conduct 2D hydrodynamics simulations of SN-companion interactions and the subsequent post-impact evolution of the companion. Our results suggest that a surviving companion becomes brighter in 2 orders of magnitude and temporarily redder after the SN impact. The companion might be detectable with the JWST NIRCam short-wavelength channel in a few years. Furthermore, the predicted magnitudes of surviving companions show a significant magnitude gradient around the peak. This could be another indicator to identify the surviving companion from an SE SN.
|
[
154,
291,
304,
1730,
767
] |
[
"binary stars",
"companion stars",
"core-collapse supernovae",
"type ic supernovae",
"hydrodynamical simulations"
] |
2023ApJ...943...30O
|
Searching for Conformity Across Cosmic Time with Local Group and Local Volume Star Formation Histories
|
Conformity denotes the correlation of properties between pairs of galaxies as a function of separation. Correlations between properties such as the star formation rate (SFR), stellar mass, and specific star formation rate (sSFR) have implications for the impact of environment upon galaxy formation and evolution. Conformity between primary galaxies and satellites within the same dark matter halo has been well documented in simulations and observations. However, the existence of conformity at greater distances-known as two-halo conformity-remains uncertain. We investigate whether galaxies in the Local Volume to a distance of 4 Mpc show conformity by examining the SFR, sSFR, stellar mass, and quenched fraction as a function of physical separation. Making use of the star formation histories of these galaxies, we then extend this analysis back in time to offer the first probe of conformity inside our past light cone. At the present day, we find that the stellar mass or sSFR of a galaxy correlates with the median SFR of neighboring galaxies at a separation of 2-3 Mpc. At a lookback time of 1 Gyr, we find a correlation with the quenched fraction of neighboring galaxies, again at a 2-3 Mpc separation. These signals of conformity likely arise from the differences between the recent star formation histories of Local Group dwarf galaxies and those outside the Local Group. As current and future missions including JWST, Rubin, and Roman expand the sample of Local Volume galaxies, tests of conformity using star formation histories will provide an important tool for exploring spatiotemporal correlations between galaxies.
|
[
594,
2029,
416
] |
[
"galaxy evolution",
"galaxy environments",
"dwarf galaxies"
] |
2023ApJ...955L..40M
|
On the Magnetic Nature of Quiet-Sun Chromospheric Grains
|
Ca II K grains, i.e., intermittent, short-lived (about 1 minute), periodic (2-4 minutes), pointlike chromospheric brightenings, are considered to be the manifestations of acoustic waves propagating upward from the solar surface and developing into shocks in the chromosphere. After the simulations of Carlsson and Stein, we know that hot shocked gas moving upward interacting with the downflowing chromospheric gas (falling down after having been displaced upward by a previous shock) nicely reproduces the spectral features of the Ca II K profiles observed in such grains, i.e., a narrowband emission-like feature at the blue side of the line core. However, these simulations are one-dimensional and cannot explain the location or the pointlike shape of the grains. Here, we report on the magnetic nature of these events. Furthermore, we report on similar events occurring at the largest flux concentrations, though they are longer-lived (up to 8 minutes) and exhibit the typical signature of steep velocity gradients traveling across the atmosphere. The spectral signatures of the studied events resemble their counterparts in sunspots, the umbral flashes. We then propose that magnetohydrodynamical waves are not only channeled through the magnetic field in sunspots, but they pervade the whole atmosphere. The propagation along magnetic fields can explain the pointlike appearance of the calcium grains observed in the quiet chromosphere.
|
[
1477,
1986,
994,
1973
] |
[
"solar atmosphere",
"quiet solar chromosphere",
"magnetic fields",
"spectropolarimetry"
] |
2021ApJ...918L..32M
|
A New Set of Chisels for Galactic Archeology: Sc, V, and Zn as Taggers of Accreted Globular Clusters
|
Chemical tagging is a powerful tool to reveal the origin of stars and globular clusters (GCs), especially when dynamics alone cannot provide robust answers. So far, mostly α-elements and neutron capture elements have been used to distinguish stars born in the Milky Way (MW) from those born in external environments such as that of dwarf galaxies. Here, instead, we use iron-peak element abundances to investigate the origin of a sample of metal-rich GCs. By homogeneously analyzing high-resolution UVES spectra of giant stars belonging to four metal-rich GCs (namely NGC 5927, NGC 6388, NGC 6441, and NGC 6496), we find that while the α-elements Si and Ca have similar abundance ratios for all four GCs, and Ti and neutron capture elements (La, Ba, and Eu) only show a marginal discrepancy, a stark difference is found when considering the abundances of some iron-peak elements (Sc, V, and Zn). In particular, NGC 6388 and NGC 6441 have abundance ratios for these iron-peak elements significantly lower (by ~0.5 dex) than those measured in NGC 5927 and NGC 6496, which are clearly identified as born in situ MW clusters through an analysis of their orbital properties. These measurements indicate that the environment in which these clusters formed is different, and they provide robust evidence supporting an accreted origin from the same progenitor for NGC 6388 and NGC 6441. <SUP>*</SUP> Based on observations collected at the ESO-VLT under programs 073.D-0211, 079.B-0721, and 193.D-0232.
|
[
1577,
656
] |
[
"stellar abundances",
"globular star clusters"
] |
2023ApJ...942...97C
|
Return of 4U 1730-22 after 49 yr Silence: The Peculiar Burst Properties of the 2021/2022 Outbursts Observed by Insight-HXMT
|
Staying in quiescence for 49 yr, 4U 1730-22 became active and had two outbursts in 2021 and 2022; 10 thermonuclear X-ray bursts were detected with Insight-HXMT. Among them, the faintest burst showed a double-peaked profile, placing the source as the seventh accreting neutron star (NS) exhibiting double-peaked type I X-ray bursts; the other bursts showed photospheric radius expansion (PRE). The properties of a double-peaked non-PRE burst indicate that it could be related to a stalled burning front. For the five bright PRE bursts, apart from the emission from the neutron star (NS) surface, we find the residuals both in the soft (<3 keV) and hard (>10 keV) X-ray bands. Time-resolved spectroscopy reveals that the excess can be attributed to an enhanced preburst/persistent emission or the Comptonization of the burst emission by the corona. We find, the burst emission shows a rise until the photosphere touches down to the NS surface rather than the theoretical predicted constant Eddington luminosity. The shortage of the burst emission in the early rising phase is beyond the occlusion by the disk. We speculate that the findings above are due to that the obscured part (not only the lower part) of the NS surface is exposed to the line of sight due to the evaporation of the obscured material by the burst emission, or the burst emission is anisotropic (ξ > 1) in the burst early phase. In addition, based on the fluxes of PRE bursts at their touchdown times, we derive a distance estimation as 9.0-12.4 kpc.
|
[
1813
] |
[
"x-ray bursters"
] |
2023ApJ...958L..37L
|
The Preexplosion Environments and the Progenitor of SN 2023ixf from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX)
|
Supernova (SN) 2023ixf was discovered on 2023 May 19. The host galaxy, M101, was observed by the Hobby-Eberly Telescope Dark Energy Experiment collaboration over the period 2020 April 30-2020 July 10, using the Visible Integral-field Replicable Unit Spectrograph (3470 ≲ λ ≲ 5540 Å) on the 10 m Hobby-Eberly Telescope. The fiber filling factor within ±30″ of SN 2023ixf is 80% with a spatial resolution of 1″. The r < 5.″5 surroundings are 100% covered. This allows us to analyze the spatially resolved preexplosion local environments of SN 2023ixf with nebular emission lines. The two-dimensional maps of the extinction and the star formation rate (SFR) surface density (Σ<SUB>SFR</SUB>) show weak increasing trends in the radial distributions within the r < 5.″5 regions, suggesting lower values of extinction and SFR in the vicinity of the progenitor of SN 2023ixf. The median extinction and that of the surface density of SFR within r < 3″ are E(B - V) = 0.06 ± 0.14, and ${{\rm{\Sigma }}}_{\mathrm{SFR}}={10}^{-5.44\pm 0.66}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}\,{\mathrm{arcsec}}^{-2}.$ There is no significant change in extinction before and after the explosion. The gas metallicity does not change significantly with the separation from SN 2023ixf. The metal-rich branch of the R <SUB>23</SUB> calculations indicates that the gas metallicity around SN 2023ixf is similar to the solar metallicity (~Z <SUB>☉</SUB>). The archival deep images from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) show a clear detection of the progenitor of SN 2023ixf in the z band at 22.778 ± 0.063 mag, but nondetections in the remaining four bands of CFHTLS (u, g, r, i). The results suggest a massive progenitor of ≈22 M <SUB>☉</SUB>.
|
[
1668
] |
[
"supernovae"
] |
2020ApJ...892....3H
|
Orbital Evidences for Dark-matter-free Milky Way Dwarf Spheroidal Galaxies
|
The nature of Milky Way dwarf spheroidals (MW dSphs) has been questioned, in particular whether they are dominated by dark matter (DM). Here we investigate an alternative scenario, for which tidal shocks are exerted by the MW to DM-free dSphs after a first infall of their gas-rich progenitors, and for which theoretical calculations have been verified by pure N-body simulations. Whether or not the dSphs are on their first infall cannot be resolved on the sole basis of their star formation history. In fact, gas removal may cause complex gravitational instabilities, and near-pericenter passages can give rise to tidal disruptive processes. Advanced precision with the Gaia satellite in determining both their past orbital motions and the MW velocity curve is, however, providing crucial results. First, tidal shocks explain why DM-free dSphs are found preferentially near their pericenter, where they are in a destructive process, while their chance to be long-lived satellites is associated with a very low probability P ∼ 2 × 10<SUP>-7</SUP>, which is at odds with the current DM-dominated dSph scenario. Second, most dSph binding energies are consistent with a first infall. Third, the MW tidal shocks that predict the observed dSph velocity dispersions are themselves predicted in amplitude by the most accurate MW velocity curve. Fourth, tidal shocks accurately predict the forces or accelerations exerted at half-light radii of dSphs, including the MW and the Magellanic System gravitational attractions. The above is suggestive of dSphs that are DM-free and tidally shocked near their pericenters, which may provoke a significant quake in our understanding of near-field cosmology.
|
[
420,
416,
1146,
353,
619,
1879,
1054,
990,
991,
929
] |
[
"dwarf spheroidal galaxies",
"dwarf galaxies",
"observational cosmology",
"dark matter",
"galaxy rotation curves",
"circumgalactic medium",
"milky way galaxy",
"magellanic clouds",
"magellanic stream",
"local group"
] |
2021ApJ...919...24B
|
Detecting Neutrino Mass by Combining Matter Clustering, Halos, and Voids
|
We quantify the information content of the nonlinear matter power spectrum, the halo mass function, and the void size function, using the Quijote N-body simulations. We find that these three statistics exhibit very different degeneracies among the cosmological parameters, and thus the combination of all three probes enables the breaking of degeneracies, in turn yielding remarkably tight constraints. We perform a Fisher analysis using the full covariance matrix, including all auto- and cross correlations, finding that this increases the information content for neutrino mass compared to a correlation-free analysis. The multiplicative improvement of the constraints on the cosmological parameters obtained by combining all three probes compared to using the power spectrum alone are: 137, 5, 8, 20, 10, and 43, for Ω<SUB>m</SUB>, Ω<SUB>b</SUB>, h, n<SUB>s</SUB>, σ<SUB>8</SUB>, and M<SUB>ν</SUB>, respectively. The marginalized error on the sum of the neutrino masses is σ(M<SUB>ν</SUB>) = 0.018 eV for a cosmological volume of $1{\left({h}^{-1}\,\mathrm{Gpc}\right)}^{3}$ , using ${k}_{\max }=0.5\,h\,{\mathrm{Mpc}}^{-1}$ , and without cosmic microwave background (CMB) priors. We note that this error is an underestimate insomuch as we do not consider super-sample covariance, baryonic effects, and realistic survey noises and systematics. On the other hand, it is an overestimate insomuch as our cuts and binning are suboptimal due to restrictions imposed by the simulation resolution. Given upcoming galaxy surveys will observe volumes spanning $\sim 100{\left({h}^{-1}\,\mathrm{Gpc}\right)}^{3}$ , this presents a promising new avenue to measure neutrino mass without being restricted by the need for accurate knowledge of the optical depth, which is required for CMB-based measurements. Furthermore, the improved constraints on other cosmological parameters, notably Ω<SUB>m</SUB>, may also be competitive with CMB-based measurements.
|
[
338,
1102,
902,
1083,
1779,
1880,
339,
340
] |
[
"cosmological neutrinos",
"neutrino masses",
"large-scale structure of the universe",
"n-body simulations",
"voids",
"galaxy dark matter halos",
"cosmological parameters",
"cosmological parameters from large-scale structure"
] |
2021ApJ...916..108Z
|
Estimating the Black Hole Spin for the X-Ray Binary MAXI J1820+070
|
MAXI J1820+070 is a newly discovered black hole X-ray binary, whose dynamical parameters, namely the black hole mass, the inclination angle, and the source distance, have recently been estimated. Insight-HXMT have observed its entire outburst from 2018 March 14. In this work, we attempted to estimate the spin parameter a<SUB>*</SUB>, using the continuum-fitting method and applying a fully relativistic thin disk model to the soft-state spectra obtained by Insight-HXMT. It is well known that a<SUB>*</SUB> is strongly dependent on three dynamical parameters in this method, and we have examined two sets of parameters. Adopting our preferred parameters: M = ${8.48}_{-0.72}^{+0.79}\,{M}_{\odot }$, i = 63° ± 3°, and D = 2.96 ± 0.33 kpc, we found a slowly spinning black hole of a<SUB>*</SUB> = 0.14 ± 0.09 (1σ), which gives a prograde spin parameter as the majority of other systems show. It is also possible for the black hole to have a retrograde spin (less than 0) if different dynamical parameters are taken.
|
[
159,
1811
] |
[
"black hole physics",
"x-ray binary stars"
] |
2020ApJ...891...14L
|
Slip-back Mapping as a Tracker of Topological Changes in Evolving Magnetic Configurations
|
The topology of the coronal magnetic field has a strong impact on the properties of the solar corona and presumably on the origin of the slow solar wind. To advance our understanding of this impact, we revisit the concept of so-called slip-back mapping and adapt it to determine open, closed, and disconnected flux systems that are formed in the solar corona by magnetic reconnection during a given time interval. In particular, the method we developed allows us to describe magnetic flux transfer between open and closed flux regions via so-called interchange reconnection with an unprecedented level of detail. We illustrate the application of this method to the analysis of the global MHD evolution of the solar corona driven by idealized differential rotation of the photospheric plasma.
|
[
1964,
1483,
1534
] |
[
"magnetohydrodynamics",
"solar corona",
"solar wind"
] |
2021AJ....161...84M
|
Revealing Short-period Exoplanets and Brown Dwarfs in the Galactic Bulge Using the Microlensing Xallarap Effect with the Nancy Grace Roman Space Telescope
|
The Nancy Grace Roman Space Telescope (Roman) will provide an enormous number of microlensing light curves with much better photometric precision than ongoing ground-based observations. Such light curves will enable us to observe high-order microlensing effects which have been previously difficult to detect. In this paper, we investigate Roman's potential to detect and characterize short-period planets and brown dwarfs (BDs) in source systems using the orbital motion of source stars, the so-called xallarap effect. We analytically estimate the measurement uncertainties of xallarap parameters using Fisher matrix analysis. We show that the Roman Galactic Exoplanet Survey can detect warm Jupiters with masses down to 0.5 M<SUB>Jup</SUB> and orbital periods of 30 days via the xallarap effect. Assuming a planetary frequency function from Cumming et al., we find Roman will detect ∼10 hot and warm Jupiters and ∼30 close-in BDs around microlensed source stars during the microlensing survey. These detections are likely to be accompanied by the measurements of the companion's masses and orbital elements, which will aid in the study of the physical properties for close-in planet and BD populations in the Galactic bulge.
|
[
672,
2139,
498,
185,
2041,
2147,
489,
1857,
753
] |
[
"gravitational microlensing",
"xallarap effect",
"exoplanets",
"brown dwarfs",
"galactic bulge",
"gravitational microlensing exoplanet detection",
"exoplanet detection methods",
"astronomical simulations",
"hot jupiters"
] |
2023ApJ...953...85B
|
Heliocentric Distance and Solar Activity Dependence of Sustained Quasi-radial Interplanetary Magnetic Field Occurrence
|
Planets close to their stars experience an interplanetary magnetic field (IMF) that is dominantly quasi-radial. Our solar system serves as a laboratory to study how the occurrence of quasi-radial IMF varies away from the star and under different stellar activities. Furthermore, on time and spatial scales relevant to magnetospheric physics, solar wind variability prevails in the form of structures generated both at the Sun and locally in the interplanetary space. The stationary Parker spiral model only approximates the large-scale structure of the IMF. Deviations from the Parker spiral often result in strongly radial magnetic fields that give rise to kinetic foreshock turbulence, which in turn can impact planetary magnetospheres. The relative significance of this type of interaction can be estimated statistically based on the occurrence rate of cases where the IMF is directed along the radial direction, leading to the entire day-side magnetosphere being downstream of the ion foreshock. We use observations covering radial distances from 0.1 to 10 au and more than 2 solar cycles to quantify the prevalence of radial IMFs throughout the heliosphere. Near Earth's orbit, it is found that the occurrence rates of quasi-radial and southward IMF orientations are similar, and that the Pearson correlation coefficient is ${{ \mathcal R }}_{{xy}}\sim -0.7$ calculated between quasi-radial IMF occurrence rate and solar activity. A negative correlation is demonstrated for radial distances extending to at least Mars but not to Saturn.
|
[
824,
1246,
1487
] |
[
"interplanetary magnetic fields",
"planetary bow shocks",
"solar cycle"
] |
2023AJ....165...53I
|
Photometry of the Four Anti-Galactocentric Old Open Clusters: Czernik 30, Berkeley 34, Berkeley 75, and Berkeley 76
|
We present a BVI photometric study of four old open clusters (OCs) in the the Milky Way, Czernik 30, Berkeley 34, Berkeley 75, and Berkeley 76 using the observation data obtained with the Small and Moderate Aperture Research Telescope System 1.0 m telescope at the Cerro Tololo Inter-American Observatory, Chile. These four OCs are located at the anti-Galactocentric direction and in the Galactic plane. We determine the fundamental physical parameters for the four OCs, such as age, metallicity, distance modulus, and color excess, using red clump and PARSEC isochrone fitting methods after finding center and size of the four OCs. These four old OCs are 2-3 Gyr old and 6-8 kpc away from the Sun. The metallicity ([Fe/H]) values of the four OCs are between -0.6 and 0.0 dex. We combine data for these four OCs with those for old OCs from five literatures resulting in 236 objects to investigate Galactic radial-metallicity distribution. The gradient of a single linear fit for this Galactocentric [Fe/H] distribution is -0.052 ± 0.004 dex kpc<SUP>-1</SUP>. If we assume the existence of a discontinuity in this radial-metallicity distribution, the gradient at Galactocentric radius <12 kpc is -0.070 ± 0.006 dex kpc<SUP>-1</SUP>, while that at the outer part is -0.016 ± 0.010 which is flatter than that of the inner part. Although there are not many sample clusters at the outer part, the broken linear fit seems to better follow the observation data.
|
[
1160,
1370,
589
] |
[
"open star clusters",
"red giant clump",
"galaxy disks"
] |
2021ApJ...913..147L
|
The Decay of α-configuration Sunspots
|
To better understand the decay of different types of sunspots, we studied the decay of eight α-configuration sunspots by using the data that were acquired by the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory. We followed their decay for about four days and analyzed the evolution of their photospheric area and magnetic field parameters. We found that the area and total magnetic flux of α sunspots show a near-linear decrease during their decay. Meanwhile, the area decay rate of an individual sunspot is not constant. The area decay of a sunspot can be divided into two stages, a slow and a rapid decay process. Moreover, according to the difference of the area decay of the penumbra and umbra, the α sunspots decay can be classified in three ways: the penumbra and umbra decay synchronously, the penumbra decays first, and the umbra decays first. In addition, the flux decay of the penumbra is lagging behind the decay of the penumbral area. This finding suggests that the vertical magnetic field of the sunspot penumbra increases significantly in the early stage of sunspot decay.
|
[
1653,
1503,
1518
] |
[
"sunspots",
"solar magnetic fields",
"solar photosphere"
] |
2024RNAAS...8..130B
|
Constrained Wave-telescope Technique
|
We revisit the mathematics behind the application of the physically informed constraint matrix used in the wave-telescope technique. The constraint matrix, used to enforce the divergence-free nature of the magnetic field when processing in situ multi-spacecraft data, is found in a few different forms in the literature. We give brief analytical and computational evidence to support a particular combination of constraint matrix and spectral energy density equation for the wave-telescope technique.
|
[
994,
2089,
38,
1965,
1544
] |
[
"magnetic fields",
"plasma physics",
"analytical mathematics",
"computational methods",
"space plasmas"
] |
2020AJ....159...46K
|
Elemental Abundances in M31: The Kinematics and Chemical Evolution of Dwarf Spheroidal Satellite Galaxies
|
We present deep spectroscopy from Keck/DEIMOS of Andromeda I, III, V, VII, and X, all of which are dwarf spheroidal satellites of M31. The sample includes 256 spectroscopic members across all five dSphs. We confirm previous measurements of the velocity dispersions and dynamical masses, and we provide upper limits on bulk rotation. Our measurements confirm that M31 satellites obey the same relation between stellar mass and stellar metallicity as Milky Way (MW) satellites and other dwarf galaxies in the Local Group. The metallicity distributions show trends with stellar mass that are similar to those of MW satellites, including evidence in massive satellites for external influence, like pre-enrichment or gas accretion. We present the first measurements of individual element ratios, like [Si/Fe], in the M31 system, as well as measurements of the average [α/Fe] ratio. The trends of [α/Fe] with [Fe/H] also follow the same galaxy mass-dependent patterns as MW satellites. Less massive galaxies have more steeply declining slopes of [α/Fe] that begin at lower [Fe/H]. Finally, we compare the chemical evolution of M31 satellites to M31's Giant Stellar Stream and smooth halo. The properties of the M31 system support the theoretical prediction that the inner halo is composed primarily of massive galaxies that were accreted early. As a result, the inner halo exhibits higher [Fe/H] and [α/Fe] than surviving satellite galaxies. <P />The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.
|
[
39,
416,
1577,
929
] |
[
"andromeda galaxy",
"dwarf galaxies",
"stellar abundances",
"local group"
] |
2023ApJ...952..132Z
|
On the Formation of Vinylamine (C<SUB>2</SUB>H<SUB>3</SUB>NH<SUB>2</SUB>) in Interstellar Ice Analogs
|
Amines-organic molecules carrying the -NH<SUB>2</SUB> moiety-have been recognized as a vital intermediate in the formation of prebiotic molecules such as amino acids and nucleobases. Here we report the formation of vinylamine (C<SUB>2</SUB>H<SUB>3</SUB>NH<SUB>2</SUB>), which was recently detected toward G+0.693-0.027, in interstellar ice analogs composed of acetylene (C<SUB>2</SUB>H<SUB>2</SUB>) and ammonia (NH<SUB>3</SUB>) exposed to energetic electrons. Our experiments mimic cascades of secondary electrons in the tracks of galactic cosmic rays impinging on interstellar ice in molecular clouds. Tunable photoionization reflectron time-of-flight mass spectrometry (PI-Re-TOF-MS), along with isomer-specific assignments, reveals the production of vinylamine (C<SUB>2</SUB>H<SUB>3</SUB>NH<SUB>2</SUB>). Quantum chemical computations suggest that both a radical-radical recombination of the amino (NH<SUB>2</SUB>) with the vinyl (C<SUB>2</SUB>H<SUB>3</SUB>) radical and a one-step concerted route are feasible pathways to vinylamine (C<SUB>2</SUB>H<SUB>3</SUB>NH<SUB>2</SUB>). The results present the first documented route to form vinylamine in interstellar ice analogs. This unsaturated amine, which is isovalent to vinylalcohol (C<SUB>2</SUB>H<SUB>3</SUB>OH), could be a key precursor for the abiotic synthesis of prebiotic molecules such as amino acids and nucleobases, with implications for the origins-of-life theme.
|
[
2079,
75,
2004,
847
] |
[
"pre-biotic astrochemistry",
"astrochemistry",
"laboratory astrophysics",
"interstellar medium"
] |
2023ApJ...947...53R
|
The Possibility of Modeling the Very High Energy Afterglow of GRB 221009A in a Wind Environment
|
In this paper, we model the dynamics and radiation physics of the rarity event GRB 221009A afterglow in detail. By introducing a top-hat jet that propagates in an environment dominated by stellar winds, we explain the publicly available observations of afterglow associated with GRB 221009A over the first week. It is predicted that GRB 221009A emits a luminous very high energy afterglow based on the synchrotron self-Compton (SSC) process in our model. We show the broadband spectral energy distribution (SED) analysis results of GRB 221009A and find that the SSC radiation component of GRB 221009A is very bright in the 0.1-10 TeV band. The integrated SED shows that the SSC emission in the TeV band has detection sensitivity significantly higher than that of LHASSO, MAGIC, and CTA. However, since the release of further observations, deviations from the standard wind environment model have gradually shown up in data. For example, the late-time multiband afterglow cannot be consistently explained under the standard wind environment scenario. It may be necessary to consider modeling with a structured jet with complex geometry or a partial revision of the standard model. Furthermore, we find that the inclusion of GeV observations could break the degeneracy between model parameters, highlighting the significance of high-energy observations in determining accurate parameters for GRB afterglows.
|
[
629,
739
] |
[
"gamma-ray bursts",
"high energy astrophysics"
] |
2023ApJ...951L...2L
|
First Detection of a Linear Structure in the Midplane of the Young HH 211 Protostellar Disk: A Spiral Arm?
|
Spiral structures have been detected in evolved protostellar disks, driving the disk accretion toward the central protostars to facilitate star formation. However, it is still unclear if these structures can form earlier in young protostellar disks. With the Atacama Large Millimeter/submillimeter Array, we have detected and spatially resolved a very young and nearly edge-on dusty disk with a radius of only ~20 au in the HH 211 protostellar system at submillimeter wavelength. It is geometrically thick, indicating that the submillimeter-light-emitting dust grains have yet to settle to the midplane for planet formation. Intriguingly, it shows three bright linear structures parallel to the equatorial plane, resembling a three-layer pancake that has not been seen before. The top and bottom ones arise from the warm disk surfaces, unveiling the flared structure of the disk. More importantly, the middle one is in the dense midplane of the disk and can be modeled as a trailing spiral arm excited by disk gravity, as seen in evolved protostellar disks, supporting the presence of spiral structures in the very early phase for disk accretion.
|
[
1569,
870,
1579
] |
[
"star formation",
"jets",
"stellar accretion disks"
] |
2023ApJ...955...69T
|
Gaia17bpp: A Giant Star with the Deepest and Longest Known Dimming Event
|
We report the serendipitous discovery of Gaia17bpp/2MASS J19372316+1759029, a binary star with a deep single large-amplitude dimming event of ~4.5 mag that lasted over 6.5 yr. Using the optical-to-IR spectral energy distribution (SED), we constrain the primary star to be a cool giant M0III star with effective temperature T <SUB>eff</SUB> = 3850 K and radius R = 58 R <SUB>⊙</SUB>. Based on the SED fitting, we obtained a bimodal posterior distribution of primary stellar masses with a stronger preference for a 1.5 M <SUB>⊙</SUB> mass star. Within the last 66 yr of photometric coverage, no other significant dimming events of this depth and duration were identified in the optical light curves. Using a Gaussian process, we fit a generalized Gaussian distribution to the optical and IR light curves and conclude that the dimming event exhibits moderate asymmetries from optical to IR. At the minimum of the dimming event, the Wide-field Infrared Survey Explorer color (W1-W2) differed by ~0.2 mag relative to the primary star color outside the dimming event. The ingress and egress colors show a shallow reddening profile. We suggest that the main culprit of the dimming event is likely due to the presence of a large, optically thick disk transiting the primary giant star. By fitting a monochromatic transit model of an oblate disk transiting a star, we found good agreement with a slow-moving (0.005 km s<SUP>-1</SUP>) disk with a ~1.4 au radius. We propose that Gaia17bpp belongs to a rare binary star population similar to the ϵ Aurigae system, which consists of a secondary star enshrouded by an optically thick debris disk.
|
[
2135,
154,
1202
] |
[
"stellar occultation",
"binary stars",
"peculiar variable stars"
] |
2022ApJ...928..133C
|
Evidence of Magnetic Reconnection with Multiple X Lines and Flux Ropes in Thin Magnetotail Currents Observed by the MMS Spacecraft: Results of Grad-Shafranov Reconstruction
|
There is some observational evidence for the existence of multiple X line magnetic reconnection (MR) in various planetary magnetotails but the overall observationally based MR topology in two or three dimensions is still not available. This study reports the first 2D structures of MR with multiple X lines and magnetic islands observed by the Magnetospheric Multiscale (MMS) spacecraft in the Earth's magnetotail based on the Grad-Shafranov (GS) reconstruction model with temperature anisotropy. The tearing mode geometry is revealed within the spatial domain of 3800 km × 800 km with multiple X lines and magnetic islands on the spatial scale of the sub-ion inertial length or a few times the electron gyroradius. The MR event is seen by all four MMS spacecraft but the magnetic islands are caught only by the MMS3 spacecraft, and exhibit large firehose-type temperature anisotropy. The GS reconstructed maps based on the MMS1, 2, and 4 show a single X line and partial ion-scale magnetic islands with a smaller degree of temperature anisotropy. The reconstruction results remain the same for various energy closures, and the firehose-type anisotropy is found to yield smaller magnetic islands than the isotropic cases, which is opposite to the previous findings for MR events with mirror-type temperature anisotropy.
|
[
1544,
1261,
2089,
997
] |
[
"space plasmas",
"plasma astrophysics",
"plasma physics",
"planetary magnetospheres"
] |
2023ApJ...957...47I
|
Effective Reaction Temperatures of Irreversible Dust Chemical Reactions in a Protoplanetary Disk
|
Dust particles in protoplanetary disks experience various chemical reactions under different physicochemical conditions through their accretion and diffusion, which results in the radial chemical gradient of dust. We performed three-dimensional Monte Carlo simulations to evaluate the dust trajectories and the progress of fictitious irreversible reactions, of which kinetics is expressed by the Johnson-Mehl-Avrami equation. The distribution of the highest temperature that each particle experiences before the degree of reaction exceeds a certain level shows the lognormal distribution, and its mode temperature was used as the effective reaction temperature. Semi-analytical prediction formulas of the effective reaction temperature and its dispersion were derived by comparing a reaction timescale with a diffusive transport timescale of dust as a function of the reaction parameters and the disk parameters. The formulas reproduce the numerical results of the effective reaction temperatures and their dispersions within 5.5% and 24%, respectively, in a wide temperature range (200-1400 K). We applied the formulas for the crystallization of amorphous silicate dust and its oxygen isotope exchange with the H<SUB>2</SUB>O vapor based on the experimentally determined kinetics. For submicron-sized amorphous forsterite dust, the predicted effective reaction temperature for the oxygen isotope exchange was lower than that of crystallization without overlap even considering their dispersions. This suggests that the amorphous silicate dust in the protosolar disk could exchange their oxygen isotopes efficiently with the <SUP>16</SUP>O-poor H<SUB>2</SUB>O vapor, resulting in the distinct oxygen isotope compositions from the Sun.
|
[
1528,
2293,
331,
75,
2271,
1300
] |
[
"solar system",
"solar system evolution",
"cosmochemistry",
"astrochemistry",
"dust composition",
"protoplanetary disks"
] |
2023AJ....165..242G
|
Retrieval Survey of Metals in Six Ultrahot Jupiters: Trends in Chemistry, Rain-out, Ionization, and Atmospheric Dynamics
|
Ground-based high-resolution spectroscopy (HRS) has detected numerous chemical species and atmospheric dynamics in exoplanets, most notably ultrahot Jupiters (UHJs). However, quantitative estimates on abundances have been challenging but are essential for accurate comparative characterization and to determine formation scenarios. In this work, we retrieve the atmospheres of six UHJs (WASP-76 b, MASCARA-4 b, MASCARA-2 b, WASP-121 b, HAT-P-70 b, and WASP-189 b) with ESPRESSO and HARPS-N/HARPS observations, exploring trends in eleven neutral species and dynamics. While Fe abundances agree well with stellar values, Mg, Ni, Cr, Mn, and V show more variation, highlighting the difficulty in using a single species as a proxy for metallicity. We find that Ca, Na, Ti, and TiO are underabundant, potentially due to ionization and/or nightside rain-out. Our retrievals also show that relative abundances between species are more robust, consistent with previous works. We perform spatially resolved and phase-resolved retrievals for WASP-76 b and WASP-121 b given their high signal-to-noise observations, and find the chemical abundances in each of the terminator regions are broadly consistent. We additionally constrain dynamics for our sample through Doppler shifts and broadening of the planetary signals during the primary eclipse, with median blueshifts between ~0.9 and 9.0 km s<SUP>-1</SUP> due to day-night winds. Furthermore, we constrain spectroscopic masses for MASCARA-2 b and HAT-P-70 b consistent with their known upper limits, but we note that these may be biased due to degeneracies. This work highlights the importance of future HRS studies to further probe differences and trends between exoplanets.
|
[
2021,
2300,
509,
2096
] |
[
"exoplanet atmospheric composition",
"atmospheric dynamics",
"extrasolar gaseous giant planets",
"high resolution spectroscopy"
] |
2022ApJ...941..167M
|
EMPRESS. VIII. A New Determination of Primordial He Abundance with Extremely Metal-poor Galaxies: A Suggestion of the Lepton Asymmetry and Implications for the Hubble Tension
|
The primordial He abundance Y <SUB>P</SUB> is a powerful probe of cosmology. Currently, Y <SUB>P</SUB> is best determined by observations of metal-poor galaxies, while there are only a few known local extremely metal-poor (<0.1Z <SUB>⊙</SUB>) galaxies (EMPGs) having reliable He/H measurements with He I λ10830 near-infrared (NIR) emission. Here we present deep Subaru NIR spectroscopy for 10 EMPGs. Combining the existing optical data, He/H values of 5 out of the 10 EMPGs are reliably derived by the Markov chain Monte Carlo algorithm. Adding the existing 3 EMPGs and 51 moderately metal-poor (0.1-0.4Z <SUB>⊙</SUB>) galaxies with reliable He/H estimates, we obtain ${Y}_{{\rm{P}}}={0.2370}_{-0.0034}^{+0.0033}$ by linear regression in the (He/H) - (O/H) plane, where we increase the number of EMPGs from three to eight anchoring He/H of the most metal-poor gas in galaxies. Although our Y <SUB>P</SUB> measurement and previous measurements are consistent, our result is slightly (~1σ) smaller due to our EMPGs. Including the existing primordial deuterium D <SUB>P</SUB> measurement, we constrain the effective number of neutrino species N <SUB>eff</SUB> and the baryon-to-photon ratio η showing ≳1-2σ tensions with the Standard Model and Planck Collaboration et al. (2020). Motivated by the tensions, we allow the degeneracy parameter of the electron neutrino ξ <SUB> e </SUB>, as well as N <SUB>eff</SUB> and η, to vary. We obtain ${\xi }_{e}={0.05}_{-0.02}^{+0.03}$ , ${N}_{\mathrm{eff}}={3.11}_{-0.31}^{+0.34}$ , and $\eta \times {10}^{10}={6.08}_{-0.06}^{+0.06}$ from the Y <SUB>P</SUB> and D <SUB>P</SUB> measurements with a prior of η taken from Planck Collaboration et al. Our constraints suggest a lepton asymmetry and allow for a high value of N <SUB>eff</SUB> within the 1σ level, which could mitigate the Hubble tension.
|
[
574,
580,
339,
151
] |
[
"galaxy abundances",
"galaxy chemical evolution",
"cosmological parameters",
"big bang nucleosynthesis"
] |
2022ApJ...940...21G
|
Change of Rankine-Hugoniot Relations during Postshock Relaxation of Anisotropic Distributions
|
Collisionless shocks channel the energy of the directed plasma flow into the heating of the plasma species and magnetic field enhancement. The kinetic processes at the shock transition cause the ion distributions just behind the shock to be nongyrotropic. Gyrotropization and subsequent isotropization occur at different spatial scales. Accordingly, for a given upstream plasma and magnetic field state, there would be different downstream states corresponding to the anisotropic and isotropic regions. Thus, at least two sets of Rankine-Hugoniot relations are needed, in general, to describe the connection of the downstream measurable parameters to the upstream ones. We establish the relation between the two sets.
|
[
2086,
829,
1246
] |
[
"shocks",
"interplanetary shocks",
"planetary bow shocks"
] |
2024ApJ...960..130T
|
Evidence of a Thick Heliopause Boundary Layer Resulting from Active Magnetic Reconnection with the Interstellar Medium
|
Voyager 1 and 2 data from the vicinity of the heliopause and very local interstellar medium are reexamined to better understand the confounding lack of rotation in the magnetic field (B-field) across the heliopause observed by both Voyagers, despite their very large spatial separations (>100 au). Using three estimates for the orientation of the B-field in the pristine interstellar medium and four models of the heliosphere, we calculate draped interstellar B-field orientations along the model heliopauses and compare those estimates to the Voyager observations. At both Voyagers, expected draped B-fields are inconsistent with the observed B-field orientations after the boundary crossings. Furthermore, we show how the longer-term trends of the observed B-fields at both Voyagers after the crossings actually rotated away from both the expected draped B-field and the pristine interstellar B-field directions. We develop evidence, including an illustrative and analogous set of observations from Magnetospheric Multiscale spacecraft along Earth's magnetopause, in support of a hypothesis that both Voyagers transited a thick boundary layer of reconnected magnetic flux along the heliopause surface. We estimate that Voyager 1 has not yet fully transited this boundary layer, the radial thickness of which at the Voyager 1 crossing location may be >18 au and likely much thicker. Meanwhile, at Voyager 2's crossing location, the boundary layer is likely much thinner, and for Voyager 2, we present evidence that Voyager 2 might already have transited the boundary layer and entered a region of fields and plasma that were never connected to the Sun-the very local interstellar medium.
|
[
707,
1576,
710,
711,
107,
847,
1261,
1964,
1504
] |
[
"heliopause",
"stellar-interstellar interactions",
"heliosheath",
"heliosphere",
"astrospheres",
"interstellar medium",
"plasma astrophysics",
"magnetohydrodynamics",
"solar magnetic reconnection"
] |
2023ApJ...956...56P
|
Deep Multimessenger Search for Compact Binary Mergers in LIGO, Virgo, and Fermi/GBM Data from 2016-2017
|
GW170817-GRB 170817A provided the first observation of gravitational waves from a neutron star merger with associated transient counterparts across the entire electromagnetic spectrum. This discovery demonstrated the long-hypothesized association between short gamma-ray bursts and neutron star mergers. More joint detections are needed to explore the relation between the parameters inferred from the gravitational wave and the properties of the gamma-ray burst signal. We developed a joint multimessenger analysis of LIGO, Virgo, and Fermi/GBM data designed for detecting weak gravitational-wave transients associated with weak gamma-ray bursts. As such, it does not start from confident (GWTC-1) events only. Instead, we take the full list of existing compact binary coalescence triggers generated with the PyCBC pipeline from the second Gravitational-Wave Observing Run (O2), and reanalyze the entire set of public Fermi/GBM data covering this observing run to generate a corresponding set of gamma-ray burst candidate triggers. We then search for coincidences between the gravitational-wave and gamma-ray burst triggers without requiring a confident detection in any channel. The candidate coincidences are ranked according to a statistic combining each candidate's strength in gravitational-wave and gamma-ray data, their time proximity, and the overlap of their sky localization. The ranking is then converted to a false alarm rate using time shifts between the gravitational-wave and gamma-ray burst triggers. We present the results using O2 triggers, which allowed us to check the validity of our method against GW170817-GRB 170817A. We also discuss the different configurations tested to maximize the significance of the joint detection.
|
[
629,
678,
1108
] |
[
"gamma-ray bursts",
"gravitational waves",
"neutron stars"
] |
2022ApJ...931..154R
|
Exploring Changes in Quasar Spectral Energy Distributions across C IV Parameter Space
|
We examine the UV/X-ray properties of 1378 quasars in order to link empirical correlations to theoretical models of the physical mechanisms dominating quasars as a function of mass and accretion rate. The clarity of these correlations is improved when (1) using C IV broad emission line equivalent width (EQW) and blueshift (relative to systemic) values calculated from high signal-to-noise ratio reconstructions of optical/UV spectra and (2) removing quasars expected to be absorbed based on their UV/X-ray spectral slopes. In addition to using the traditional C IV parameter space measures of C IV EQW and blueshift, we define a "C IV ∥ distance" along a best-fit polynomial curve that incorporates information from both C IV parameters. We find that the C IV ∥ distance is linearly correlated with both the optical-to-X-ray slope, α <SUB>ox</SUB>, and broad-line He II EQW, which are known spectral energy distribution indicators, but does not require X-ray or high spectral resolution UV observations to compute. The C IV ∥ distance may be a better indicator of the mass-weighted accretion rate, parameterized by L/L <SUB>Edd</SUB>, than the C IV EQW or blueshift alone, as those relationships are known to break down at the extrema. Conversely, there is only a weak correlation with the X-ray energy index (Γ), an alternate L/L <SUB>Edd</SUB> indicator. We find no X-ray or optical trends in the direction perpendicular to the C IV distance that could be used to reveal differences in accretion disk, wind, or corona structure that could be widening the C IV EQW-blueshift distribution. A different parameter (such as metallicity) not traced by these data must come into play.
|
[
1319,
2129,
159,
2035
] |
[
"quasars",
"spectral energy distribution",
"black hole physics",
"x-ray active galactic nuclei"
] |
2021ApJS..256...34C
|
Classifying Seyfert Galaxies with Deep Learning
|
The traditional classification for a subclass of the Seyfert galaxies is visual inspection or using a quantity defined as a flux ratio between the Balmer line and forbidden line. One algorithm of deep learning is the convolution neural network (CNN), which has shown successful classification results. We build a one-dimensional CNN model to distinguish Seyfert 1.9 spectra from Seyfert 2 galaxies. We find that our model can recognize Seyfert 1.9 and Seyfert 2 spectra with an accuracy of over 80% and pick out an additional Seyfert 1.9 sample that was missed by visual inspection. We use the new Seyfert 1.9 sample to improve the performance of our model and obtain a 91% precision of Seyfert 1.9. These results indicate that our model can pick out Seyfert 1.9 spectra among Seyfert 2 spectra. We decompose the Hα emission line of our Seyfert 1.9 galaxies by fitting two Gaussian components and derive the line width and flux. We find that the velocity distribution of the broad Hα component of the new Seyfert 1.9 sample has an extending tail toward the higher end, and the luminosity of the new Seyfert 1.9 sample is slightly weaker than the original Seyfert 1.9 sample. This result indicates that our model can pick out the sources that have a relatively weak broad Hα component. In addition, we check the distributions of the host galaxy morphology of our Seyfert 1.9 samples and find that the distribution of the host galaxy morphology is dominated by a large bulge galaxy. In the end, we present an online catalog of 1297 Seyfert 1.9 galaxies with measurements of the Hα emission line.
|
[
17,
1447,
1145,
2171,
205
] |
[
"active galaxies",
"seyfert galaxies",
"observational astronomy",
"galaxy spectroscopy",
"catalogs"
] |
2022ApJ...936..182W
|
Black Hole Hyperaccretion in Collapsars. III. GRB Timescale
|
Gamma-ray bursts (GRBs) are classified into long and short populations (i.e., LGRBs and SGRBs) based on the observed bimodal distribution of duration T <SUB>90</SUB>. Multimessenger observations indicate that most SGRBs and LGRBs should be powered by ultrarelativistic jets launched from black hole (BH) hyperaccretion in compact-object mergers and massive collapsars, respectively. However, the duration criterion sometimes cannot correctly reflect the physical origin of a particular GRB. In the collapsar scenario, a GRB can be observed when the jet breaks out from the envelope and circumstellar medium successfully. The observed GRB duration reflects only the time the engine operates after the jet breaks out. This work studies the propagation of jets driven by the neutrino annihilation or Blandford-Znajek mechanism in massive collapsars. The signatures of the progenitors producing LGRBs, SGRBs, and failed GRBs in the collapsar scenario are exhibited. The competition between the mass supply onto the BH hyperaccretion and jet propagation into the envelope is definitely dependent on the density profiles of the collapsars. We show that duration and isotropic energy E <SUB> γ,iso</SUB> of GRBs can help constrain the density profiles of collapsars. Finally, we propose that a collapsar-origin SGRB, GRB 200826A, might originate from a neutrino-annihilation-dominated jet launched by a ~10 M <SUB>⊙</SUB> collapsar whose progenitor's envelope has been stripped.
|
[
1390,
162,
14,
629
] |
[
"relativistic jets",
"black holes",
"accretion",
"gamma-ray bursts"
] |
2023ApJS..268...22B
|
Electron-impact Excitation of Pt I-III: The Importance of Metastables and Collision Processes in Neutron Star Merger and Laboratory Plasmas
|
The detection of a gravitational-wave signal and subsequent electromagnetic transient from a neutron star merger in 2017 is consistent with expectations of neutron star mergers as an r-process element production site. Within the first few days post-merger, the kilonova spectra are consistent with a blackbody illuminating a mix of heavy, r-process elements. With increasing time, the kilonova transitions to the non-LTE regime where the level populations and ionization balance are determined by both collisional and photoprocesses. Detailed cross section data for electron-impact processes involving the relevant species are often not available. In such circumstances, it is reasonable to use approximate methods as baseline data for use in spectral modeling, and it is useful to evaluate the accuracy of such methods against more sophisticated collision calculations when possible. We describe new calculations of the electron-impact excitation cross sections of Pt I-III using the DARC R-matrix codes. Using collisional-radiative models, we show that, at plasma conditions expected in kilonovae, the expressions of van Regemorter and Axelrod are insufficient for producing electron-impact excitation data for complex, heavy species such as the low charge states of Pt. Through comparisons with data generated with the relativistic distorted wave approach, as implemented in the Flexible Atomic Code, we show the distorted wave method produces cross section data that, when incorporated into spectral models, predicts strong spectral feature distributions similar in intensity to those from models built on data computed with the R-matrix approach for the considered ions and plasma conditions.
|
[
2219,
2065,
2004
] |
[
"electron impact excitation",
"collision physics",
"laboratory astrophysics"
] |
2023ApJ...956...65B
|
Systematic Uncertainties of Atomic Data in Photoionization Modeling
|
Fitting plasma models to high-quality spectra is a crucial tool for deriving diagnostics about the physical conditions in various astrophysical sources. Despite decades of model development, this prescription often provides an unsatisfying description of observational data. We explore some of the origins of the failure of fits of photoionized plasma models to high-resolution X-ray spectra. In particular, we test whether systematic uncertainties in underlying atomic data can account for data model discrepancies, and whether including model uncertainties during spectral fitting can provide statistically acceptable fits and reasonable parameter estimates. We fit Chandra/HETG spectra of NGC 3783 with the photoionized absorber model warmabs. We use the remaining data model discrepancies to estimate the systematic uncertainties of bound-bound radiative rates for individual transitions quantitatively. We then include these uncertainties into warmabs to return a total model uncertainty. We find residual data model discrepancies which are due to systematic errors that cannot be accounted for solely by a modification of the optical depth of strong absorption lines. Furthermore, statistical uncertainties still dominate the fit statistics. The relevance of model uncertainties in spectral fitting will vary on a case-by-case basis. However, they are likely to have a minor effect on most of the currently existing data sets. We conclude that while the quality of atomic data does have an effect on fitting photoionization models, and so demands further improvement, uncertainties in radiative rates cannot be held solely responsible for statistically unacceptable fits. Other sources of systematic uncertainties are likely to be of comparable importance and require further investigation.
|
[
2004,
2216,
2217,
2060
] |
[
"laboratory astrophysics",
"atomic data",
"atomic reactions",
"photoionization"
] |
2021ApJ...921...61L
|
Localized Acceleration of Energetic Particles by a Weak Shock in the Solar Corona
|
Globally propagating shocks in the solar corona have long been studied to quantify their involvement in the acceleration of energetic particles. However, this work has tended to focus on large events associated with strong solar flares and fast coronal mass ejections (CMEs), where the waves are sufficiently fast to easily accelerate particles to high energies. Here we present observations of particle acceleration associated with a global wave event which occurred on 2011 October 1. Using differential emission measure analysis, the global shock wave was found to be incredibly weak, with an Alfvén Mach number of ~1.008-1.013. Despite this, spatially resolved type III radio emission was observed by the Nançay RadioHeliograph at distinct locations near the shock front, suggesting localized acceleration of energetic electrons. Further investigation using magnetic field extrapolation identified a fan structure beneath a magnetic null located above the source active region, with the erupting CME contained within this topological feature. We propose that a reconfiguration of the coronal magnetic field driven by the erupting CME enabled the weak shock to accelerate particles along field lines initially contained within the fan and subsequently opening into the heliosphere, producing the observed type III emission. These results suggest that even weak global shocks in the solar corona can accelerate energetic particles via reconfiguration of the surrounding magnetic field.
|
[
1476,
1483,
1995,
1993
] |
[
"solar physics",
"solar corona",
"solar coronal waves",
"solar coronal radio emission"
] |
2023ApJ...943..151G
|
ALMA Resolves the First Strongly Lensed Optical/Near-IR-dark Galaxy
|
We present high-resolution (≲0.″1) Atacama Large Millimeter/submillimeter Array observations of the strongly lensed galaxy HATLASJ113526.2-01460 at redshift z ~ 3.1, discovered in the GAMA 12th field of the Herschel-ATLAS survey. This gravitationally lensed system is remarkably peculiar, in that neither the background source nor the foreground lens show a clearly detected optical/near-IR Hubble Space Telescope-J band emission. We perform accurate lens modeling and source morphology reconstruction in three different (sub)millimeter continuum bands and in the C[II] and CO(8-7) spectral lines. The modeling indicates a foreground lensing (likely elliptical) galaxy with mass ≳10<SUP>11</SUP> M <SUB>⊙</SUB> at z ≳ 1.5, while the source (sub)millimeter continuum and line emissions are amplified by factors μ ~ 6-13. We estimate extremely compact sizes-≲0.5 kpc for the star-forming region and ≲1 kpc for the gas component-with no clear evidence of rotation or ongoing merging events. We perform broadband SED fitting and retrieve the intrinsic demagnified physical properties of the source, which is found to feature a very high star formation rate, ≳10<SUP>3</SUP> M <SUB>⊙</SUB> yr<SUP>-1</SUP>, which, given the compact sizes, is on the verge of the Eddington limit for starbursts; the radio luminosity at 6 cm from the available EVLA observations is consistent with star formation activity. The galaxy is found to be extremely rich in gas ~10<SUP>11</SUP> M <SUB>⊙</SUB> and dust ≳10<SUP>9</SUP> M <SUB>⊙</SUB>. The stellar content ≲10<SUP>11</SUP> M <SUB>⊙</SUB> places the source well above the main sequence of star-forming galaxies, indicating that the starburst is rather young, with an estimated age ~10<SUP>8</SUP> yr. Our results indicate that the overall properties of HATLASJ113526.2-01460 are consistently explained by in situ galaxy formation and evolution scenarios.
|
[
1643,
734,
595,
1647
] |
[
"strong gravitational lensing",
"high-redshift galaxies",
"galaxy formation",
"submillimeter astronomy"
] |
2021ApJ...910..101J
|
Variation of Broad Emission Lines from QSOs with Optical/UV Periodicity to Test the Interpretation of Supermassive Binary Black Holes
|
Periodic quasars have been suggested to host supermassive binary black holes (BBHs) in their centers, and their optical/UV periodicities are interpreted as caused by either the Doppler-boosting (DB) effect of continuum emission from the disk around the secondary black hole (BH) or intrinsic accretion rate variation. However, no other definitive evidence has been found to confirm such a BBH interpretation(s). In this paper, we investigate the responses of broad emission lines (BELs) to the continuum variations for these quasars under two BBH scenarios and check whether they can be distinguished from each other and from that of a single BH system. We assume a simple circumbinary broad-line region (BLR) model, compatible with BLR size estimates, with a standard Γ distribution of BLR clouds. We find that BELs may change significantly and periodically under the BBH scenarios due to (1) the position variation of the secondary BH and (2) the DB effect, if significant, and/or intrinsic variation, which is significantly different from the case of a single BH system. For the two BBH scenarios, the responses of BELs to (apparent) continuum variations, caused by the DB effect or intrinsic rate variation, are also significantly different from each other, mainly because the DB effect has a preferred direction along the direction of motion of the secondary BH, while that due to intrinsic variation does not. Such differences in the responses of BELs from different scenarios may offer a robust way to distinguish different interpretations of periodic quasars and to identify BBHs, if any, in these systems.
|
[
159,
401,
1319,
2019,
1663,
2109
] |
[
"black hole physics",
"doppler shift",
"quasars",
"reverberation mapping",
"supermassive black holes",
"time domain astronomy"
] |
2021ApJ...916L..17W
|
Accretion-modified Stars in Accretion Disks of Active Galactic Nuclei: Gravitational-wave Bursts and Electromagnetic Counterparts from Merging Stellar Black Hole Binaries
|
The recent advanced LIGO/Virgo detections of gravitational waves (GWs) from stellar binary black hole (BBH) mergers, in particular GW190521, which is potentially associated with a quasar, have stimulated renewed interest in active galactic nuclei as factories of merging BBHs. Compact objects evolving from massive stars are unavoidably enshrouded by a massive envelope to form accretion-modified stars (AMSs) in the dense gaseous environment of a supermassive black hole (SMBH) accretion disk. We show that most AMSs form binaries due to gravitational interaction with each other during radial migration in the SMBH disk, forming BBHs inside the AMS. When a BBH is born, its orbit is initially governed by the tidal torque of the SMBH. Bondi accretion onto a BBH at a hyper-Eddington rate naturally develops and then controls the evolution of its orbits. We find that Bondi accretion leads to efficient removal of the orbital angular momentum of the binary, whose final merger produces a GW burst. Meanwhile, the Blandford-Znajek mechanism pumps the spin energy of the merged BH to produce an electromagnetic counterpart (EMC). Moreover, hyper-Eddington accretion onto the BBH develops powerful outflows and triggers a Bondi explosion, which manifests itself as an EMC of the GW burst, depending on the viscosity of the accretion flow. Thermal emission from the Bondi sphere appears as one of the EMCs. The BBHs radiate GWs with frequencies of ~10<SUP>2</SUP> Hz, which are accessible to LIGO.
|
[
16,
1663
] |
[
"active galactic nuclei",
"supermassive black holes"
] |
2021ApJ...914...69C
|
Light Curves of Partial Tidal Disruption Events
|
Tidal disruption events (TDEs) can uncover the quiescent black holes (BHs) at the center of galaxies and also offer a promising method to study them. In a partial TDE (PTDE), the BH's tidal force cannot fully disrupt the star, so the stellar core survives and only a varied portion of the stellar mass is bound to the BH and feeds it. We calculate the event rate of PTDEs and full TDEs (FTDEs). In general, the event rate of PTDEs is higher than that of FTDEs, especially for the larger BHs, and the detection rate of PTDEs is approximately dozens per year, as observed by the Zwicky Transient Factory. During the circularization process of the debris stream in PTDEs, no outflow can be launched due to the efficient radiative diffusion. The circularized debris ring then experiences viscous evolution and forms an accretion disk. We calculate the light curves of PTDEs contributed by these two processes, along with their radiation temperature evolution. The light curves have double peaks and peak in the UV spectra. Without obscuration or reprocessing of the radiation by an outflow, PTDEs provide a clean environment to study the circularization and transient disk formation in TDEs.
|
[
14,
159,
609
] |
[
"accretion",
"black hole physics",
"galaxy nuclei"
] |
2020ApJ...890..141O
|
Average Radial Structures of Gas Convection in the Solar Granulation
|
Gas convection is observed in the solar photosphere as granulation, I.e., having highly time-dependent cellular patterns, consisting of numerous bright cells called granules and dark surrounding channels called intergranular lanes. Many efforts have been made to characterize the granulation, which may be used as an energy source for various types of dynamical phenomena. Although the horizontal gas flow dynamics in intergranular lanes may play a vital role, they are poorly understood. This is because the Doppler signals can be obtained only at the solar limb, where the signals are severely degraded by a foreshortening effect. To reduce such a degradation, we use Hinode's spectroscopic data, which are free from a seeing-induced image degradation, and improve the image quality by correcting for stray light in the instruments. The data set continuously covers from the solar disk to the limb, providing a multidirectional line-of-sight (LOS) diagnosis against the granulation. The obtained LOS flow-field variation across the disk indicates a horizontal flow speed of 1.8-2.4 km s<SUP>-1</SUP>. We also derive the spatial distribution of the horizontal flow speed, which is 1.6 km s<SUP>-1</SUP> in granules and 1.8 km s<SUP>-1</SUP> in intergranular lanes, and where the maximum speed is inside intergranular lanes. This result newly suggests the following sequence of horizontal flow: a hot rising gas parcel is strongly accelerated from the granular center, even beyond the transition from the granules to the intergranular lanes, resulting in the fastest speed inside the intergranular lanes, and the gas may also experience decelerations in the intergranular lane.
|
[
101,
1322,
1518,
1875
] |
[
"astrophysical fluid dynamics",
"quiet sun",
"solar photosphere",
"solar granules"
] |
2020ApJ...904...23K
|
Dual AGN Candidates with Double-peaked [O III] Lines Matching that of Confirmed Dual AGNs
|
We have performed a spectral decomposition to search for dual active galactic nuclei (DAGNs) in the Sloan Digital Sky Survey (SDSS) quasars with z < 0.25. Potential DAGN candidates are searched by referencing velocity offsets and spectral shapes of double-peaked [O III] lines of known DAGNs. Out of 1271 SDSS quasars, we have identified 77 DAGN candidates. Optical and mid-infrared (MIR) diagnostic diagrams are used to investigate the ionizing source in the DAGN candidates. The optical diagnostic analysis suggests 93% of them are powered by AGNs, and MIR diagnostic analysis suggests 97% are powered by AGNs. About one-third of the SDSS images of the DAGN candidates show signs of tidal interaction, but we are unable to identify double nuclei in most of them due to the low spatial resolution of the archival imaging data available for most of the sample. The radio-loud fraction of the DAGN candidates (∼10%) is similar to that of typical AGNs.
|
[
16,
162,
594
] |
[
"active galactic nuclei",
"black holes",
"galaxy evolution"
] |
2023ApJ...954..194Y
|
Flare Duty Cycle of Gamma-Ray Blazars and Implications for High-energy Neutrino Emission
|
Gamma-ray flares of blazars may be accompanied by high-energy neutrinos due to interactions of high-energy cosmic rays in the jet with photons, as suggested by the detection of the high-energy neutrino IceCube-170922A during a major gamma-ray flare from blazar TXS 0506+056 at the ~3σ significance level. In this work, we present a statistical study of gamma-ray emission from blazars to constrain the contribution of gamma-ray flares to their neutrino output. We construct weekly binned light curves for 145 gamma-ray bright blazars in the Fermi Large Area Telescope Monitored Source List adding TXS 0506+056. We derive the fraction of time spent in the flaring state (flare duty cycle) and the fraction of energy released during each flare from the light curves with a Bayesian blocks algorithm. We find that blazars with lower flare duty cycles and energy fractions are more numerous among our sample. We identify a significant difference in flare duty cycles between blazar subclasses at a significance level of 5%. Then using a general scaling relation for the neutrino and gamma-ray luminosities, ${L}_{\nu }\propto {({L}_{\gamma })}^{\gamma }$ with a weighting exponent of γ = 1.0-2.0, normalized to the quiescent gamma-ray or X-ray flux of each blazar, we evaluate the neutrino energy flux of each gamma-ray flare. The gamma-ray flare distribution indicates that blazar neutrino emission may be dominated by flares for γ ≳ 1.5. The neutrino energy fluxes for 1 week and 10 yr bins are compared with the decl.-dependent IceCube sensitivity to constrain the standard neutrino emission models for gamma-ray flares. Finally, we present the upper-limit contribution of blazar gamma-ray flares to the isotropic diffuse neutrino flux.
|
[
164,
628,
739,
1100
] |
[
"blazars",
"gamma-ray astronomy",
"high energy astrophysics",
"neutrino astronomy"
] |
2023PSJ.....4..133L
|
The Timeline of Early Lunar Bombardment Constrained by the Evolving Distributions of Differently Aged Melt
|
The timeline of the early lunar bombardment remains unclear. The bombardment rate as a function of time is commonly modeled by three types of shapes: tail-end, sawtooth, and terminal cataclysm. Differently aged melt records the occurrence time of impact events and thus is crucial for constraining the timeline of the early lunar bombardment. Based on a spatially resolved numerical model, we simulate the evolving distribution of differently aged melt with a long-term impact mixing, where different shapes of impact rate function are considered. We compare the outcome of melt age distribution from different scenarios with the actual data from the lunar meteorites and the returned samples. The results suggest that, if the present data are representative of the melt age distribution on the Moon, the shape of the impact rate function is more likely comparable to the tail-end over the sawtooth and the terminal cataclysm, with the terminal cataclysm being least likely. In addition, using state-of-the-art U-Pb dating techniques, more abundant ancient basin melt is likely to be found in returned samples.
|
[
436,
949,
2299,
2238,
1038
] |
[
"earth-moon system",
"lunar craters",
"impact gardening",
"monte carlo methods",
"meteorites"
] |
2020PSJ.....1...52A
|
The Population of Kilometer-scale Retrograde Jovian Irregular Moons
|
We have searched a 2010 archival data set from the Canada-France-Hawaii Telescope for very small (km-scale) irregular moons of Jupiter in order to constrain the size distribution of these moons down to radii of ∼400 m, discovering 52 objects that are moving with Jupiter-like on-sky rates and are nearly certainly irregular moons. The four brightest detections, and seven in total, were all then linked to known Jovian moons. Extrapolating our characterized detections (those down to magnitude m<SUB>r</SUB> = 25.7) to the entire retrograde circum-Jovian population, we estimate the population of radius >0.4 km moons to be 600 (within a factor of 2). At the faintest magnitudes, we find a relatively shallow luminosity function of exponential index α = 0.29 ± 0.15, corresponding to a differential diameter power law of index q ≃ 2.5.
|
[
872,
1089,
2027,
873
] |
[
"jovian satellites",
"natural satellites (solar system)",
"irregular satellites",
"jupiter"
] |
2023ApJ...957...50J
|
Quijote-PNG: The Information Content of the Halo Mass Function
|
We study signatures of primordial non-Gaussianity (PNG) in the redshift-space halo field on nonlinear scales using a combination of three summary statistics, namely, the halo mass function (HMF), power spectrum, and bispectrum. The choice of adding the HMF to our previous joint analysis of the power spectrum and bispectrum is driven by a preliminary field-level analysis, in which we train graph neural networks on halo catalogs to infer the PNG f <SUB>NL</SUB> parameter. The covariance matrix and the responses of our summaries to changes in model parameters are extracted from a suite of halo catalogs constructed from the QUIJOTE-PNG N-body simulations. We consider the three main types of PNG: local, equilateral, and orthogonal. Adding the HMF to our previous joint analysis of the power spectrum and bispectrum produces two main effects. First, it reduces the equilateral f <SUB>NL</SUB> predicted errors by roughly a factor of 2 while also producing notable, although smaller, improvements for orthogonal PNG. Second, it helps break the degeneracy between the local PNG amplitude, ${f}_{\mathrm{NL}}^{\mathrm{local}}$ , and assembly bias, b <SUB> ϕ </SUB>, without relying on any external prior assumption. Our final forecasts for the PNG parameters are ${\rm{\Delta }}{f}_{\mathrm{NL}}^{\mathrm{local}}=40$ , ${\rm{\Delta }}{f}_{\mathrm{NL}}^{\mathrm{equil}}=200$ , ${\rm{\Delta }}{f}_{\mathrm{NL}}^{\mathrm{ortho}}=85$ , on a cubic volume of $1{\left(\mathrm{Gpc}/{\rm{h}}\right)}^{3}$ , with a halo number density of $\bar{n}\sim 5.1\,\times \,{10}^{-5}\,{h}^{3}\,{\mathrm{Mpc}}^{-3}$ , at z = 1, and considering scales up to ${k}_{\max }=0.5\,h\,{\mathrm{Mpc}}^{-1}$ .
|
[
902,
1116,
1922
] |
[
"large-scale structure of the universe",
"non-gaussianity",
"fisher's information"
] |
2020ApJ...902...24D
|
Short-term Variability of Evolved Massive Stars with TESS. II. A New Class of Cool, Pulsating Supergiants
|
Massive stars briefly pass through the yellow supergiant (YSG) phase as they evolve redward across the H-R diagram and expand into red supergiants (RSGs). Higher-mass stars pass through the YSG phase again as they evolve blueward after experiencing significant RSG mass loss. These post-RSG objects offer us a tantalizing glimpse into which stars end their lives as RSGs and why. One telltale sign of a post-RSG object may be an instability to pulsations, depending on the star's interior structure. Here we report the discovery of five YSGs with pulsation periods faster than 1 day, found in a sample of 76 cool supergiants observed by the Transiting Exoplanet Survey Satellite at a two-minute cadence. These pulsating YSGs are concentrated in an H-R diagram region not previously associated with pulsations; we conclude that this is a genuine new class of pulsating star, fast yellow pulsating supergiants (FYPSs). For each FYPS, we extract frequencies via iterative prewhitening and conduct a time-frequency analysis. One FYPS has an extracted frequency that is split into a triplet, and the amplitude of that peak is modulated on the same timescale as the frequency spacing of the triplet; neither rotation nor binary effects are likely culprits. We discuss the evolutionary status of FYPS and conclude that they are candidate post-RSGs. All stars in our sample also show the same stochastic low-frequency variability found in hot OB stars and attributed to internal gravity waves. Finally, we find four α Cygni variables in our sample, of which three are newly discovered.
|
[
732,
481,
1661,
918,
1625,
1375,
1078,
1918,
1959,
73,
1583,
1828
] |
[
"massive stars",
"evolved stars",
"supergiant stars",
"light curves",
"stellar pulsations",
"red supergiant stars",
"multi-periodic pulsation",
"wavelet analysis",
"lomb-scargle periodogram",
"asteroseismology",
"stellar astronomy",
"yellow hypergiant stars"
] |
2020ApJ...901....9H
|
Variability in Protoplanetary Nebulae: VII. Light-curve Studies of Five Medium-bright, Oxygen-rich, or Mixed-chemistry Post-AGB/Post-RGB Objects
|
We have monitored over a 10-year interval the light variations of five evolved stars with very large mid-infrared excesses. All five objects appear to have oxygen-rich or mixed oxygen-rich and carbon-rich chemistries. They all vary in light: four over a small range of ∼0.2 mag and the fifth over a larger range of ∼0.7 mag. Spectral types range from G2 to B0. Periodic pulsations are found for the first time in the three cooler ones, IRAS 18075-0924 (123 days), 19207+2023 (96 days), and 20136+1309 (142 days). No significant periodicity is found in the hotter ones, but they appear to vary on a shorter timescale of a few days or less. Two also show some evidence of longer-term periodic variations (∼4 yr). Three appear to be protoplanetary nebulae (PPNe), in the post-asymptotic giant branch (post-AGB) phase of stellar evolution. Their light variations are in general agreement with the relationships among temperature, pulsation period, and pulsation amplitude found in previously studied PPNe. The other two, however, appear to have too low a luminosity (1000-1500 L<SUB>⊙</SUB>), based on Gaia distances, to be in the post-AGB phase. Instead, they appear to be Milky Way analogs of the recently identified class of dusty post-red giant branch (post-RGB) stars found in the Magellanic Clouds, which likely had their evolution interrupted by interaction with a binary companion. If this is the case, then these would be among the first dusty post-RGB objects identified in the the Milky Way.
|
[
1301,
2121,
1625,
1307,
1078,
236,
241
] |
[
"protoplanetary nebulae",
"post-asymptotic giant branch stars",
"stellar pulsations",
"pulsating variable stars",
"multi-periodic pulsation",
"circumstellar dust",
"circumstellar matter"
] |
2020ApJ...900...28C
|
MINESweeper: Spectrophotometric Modeling of Stars in the Gaia Era
|
We present MINESweeper, a tool to measure stellar parameters by jointly fitting observed spectra and broadband photometry to model isochrones and spectral libraries. This approach enables the measurement of spectrophotometric distances, in addition to stellar parameters such as T<SUB>eff</SUB>, $\mathrm{log}g$, [Fe/H], [α/Fe], and radial velocity. MINESweeper employs a Bayesian framework and can easily incorporate a variety of priors, including Gaia parallaxes. Mock data are fit in order to demonstrate how the precision of derived parameters depends on evolutionary phase and signal-to-noise ratio. We then fit a selection of data in order to validate the model outputs. Fits to a variety of benchmark stars including Procyon, Arcturus, and the Sun result in derived stellar parameters that are in good agreement with the literature. We then fit combined spectra and photometry of stars in the open and globular clusters M92, M13, M3, M107, M71, and M67. Derived distances, [Fe/H], [α/Fe], and $\mathrm{log}g$-T<SUB>eff</SUB> relations are in overall good agreement with literature values, although there are trends between metallicity and $\mathrm{log}g$ within clusters that point to systematic uncertainties at the ≈0.1 dex level. Finally, we fit a large sample of stars from the H3 Spectroscopic Survey in which high-quality Gaia parallaxes are also available. These stars are fit without the Gaia parallaxes so that the geometric parallaxes can serve as an independent test of the spectrophotometric distances. Comparison between the two reveals good agreement within their formal uncertainties after accounting for the Gaia zero-point uncertainties.
|
[
1621,
1624,
1630,
1597,
1590,
1581,
1609,
1614,
1626,
1577,
1595,
2046
] |
[
"stellar physics",
"stellar properties",
"stellar spectral lines",
"stellar effective temperatures",
"stellar colors",
"stellar ages",
"stellar luminosities",
"stellar masses",
"stellar radii",
"stellar abundances",
"stellar distance",
"stellar evolutionary models"
] |
2024ApJ...970L..20R
|
Constraining Possible γ-Ray Burst Emission from GW230529 Using Swift-BAT and Fermi-GBM
|
GW230529 is the first compact binary coalescence detected by the LIGO–Virgo–KAGRA collaboration with at least one component mass confidently in the lower mass gap, corresponding to the range 3–5 M <SUB>⊙</SUB>. If interpreted as a neutron star–black hole merger, this event has the most symmetric mass ratio detected so far and therefore has a relatively high probability of producing electromagnetic (EM) emission. However, no EM counterpart has been reported. At the merger time t <SUB>0</SUB>, Swift-BAT and Fermi-GBM together covered 100% of the sky. Performing a targeted search in a time window [t <SUB>0</SUB> ‑ 20 s, t <SUB>0</SUB> + 20 s], we report no detection by the Swift-BAT and Fermi-GBM instruments. Combining the position-dependent γ-ray flux upper limits and the gravitational-wave posterior distribution of luminosity distance, sky localization, and inclination angle of the binary, we derive constraints on the characteristic luminosity and structure of the jet possibly launched during the merger. Assuming a top-hat jet structure, we exclude at 90% credibility the presence of a jet that has at the same time an on-axis isotropic luminosity ≳10<SUP>48</SUP> erg s<SUP>‑1</SUP> in the bolometric band 1 keV–10 MeV and a jet opening angle ≳15°. Similar constraints are derived by testing other assumptions about the jet structure profile. Excluding GRB 170817A, the luminosity upper limits derived here are below the luminosity of any GRB observed so far.
|
[
739,
628,
629,
678
] |
[
"high energy astrophysics",
"gamma-ray astronomy",
"gamma-ray bursts",
"gravitational waves"
] |
2021ApJ...920...62N
|
The Physics of the Coronal-line Region for Galaxies in Mapping Galaxies at Apache Point Observatory
|
The fundamental nature and extent of the coronal-line region (CLR), which may serve as a vital tracer for active galactic nucleus (AGN) activity, remain unresolved. Previous studies suggest that the CLR is produced by AGN-driven outflows and occupies a distinct region between the broad-line region and the narrow-line region, which places it tens to hundreds of parsecs from the galactic center. Here, we investigate 10 coronal line (CL; ionization potential ≳100 eV) emitting galaxies from the Sloan Digital Sky Survey IV Mapping Galaxies at Apache Point Observatory (MaNGA) catalog with emission from one or more CLs detected at ≥5σ above the continuum in at least 10 spaxels-the largest such MaNGA catalog. We find that the CLR is far more extended, reaching out to 1.3-23 kpc from the galactic center. We crossmatch our sample of 10 CL galaxies with the largest existing MaNGA AGN catalog and identify seven in it; two of the remaining three are galaxy mergers and the final one is an AGN candidate. Further, we measure the average CLR electron temperatures as ranging between 12,331 and 22,530 K, slightly above the typical threshold for pure AGN photoionization (~20,000 K) and indicative of shocks (e.g., merger induced or from supernova remnants) in the CLR. We reason that ionizing photons emitted by the central continuum source (i.e., AGN photoionization) primarily generate the CLs, and that energetic shocks are an additional ionization mechanism that likely produce the most extended CLRs we measure.
|
[
16,
2060,
459
] |
[
"active galactic nuclei",
"photoionization",
"emission line galaxies"
] |
2022RNAAS...6..153P
|
Approximate Relation Between Integral Albedo and Single-scattering Albedo of the Particulate Media
|
The radiative transfer model makes it possible to establish relationships between the single scattering albedo and the integral albedo of a medium consisting of particles. In this paper, an approximation is proposed for solving the inverse problem-calculating the albedo of a single scattering of a particle, based on the known value of the integral albedo. This approximation can be useful to all researchers involved in the photometry of solar system bodies with regolith-like surfaces.
|
[
1335
] |
[
"radiative transfer"
] |
2021ApJ...912...97H
|
What Causes Faint Solar Coronal Jets from Emerging Flux Regions in Coronal Holes?
|
Using EUV images and line-of-sight magnetograms from Solar Dynamics Observatory, we examine eight emerging bipolar magnetic regions (BMRs) in central-disk coronal holes for whether the emerging magnetic arch made any noticeable coronal jets directly, via reconnection with ambient open field as modeled by Yokoyama & Shibata. During emergence, each BMR produced no obvious EUV coronal jet of normal brightness, but each produced one or more faint EUV coronal jets that are discernible in AIA 193 &angst; images. The spires of these jets are much fainter and usually narrower than for typical EUV jets that have been observed to be produced by minifilament eruptions in quiet regions and coronal holes. For each of 26 faint jets from the eight emerging BMRs, we examine whether the faint spire was evidently made a la Yokoyama & Shibata. We find that (1) 16 of these faint spires evidently originate from sites of converging opposite-polarity magnetic flux and show base brightenings like those in minifilament-eruption-driven coronal jets, (2) the 10 other faint spires maybe were made by a burst of the external-magnetic-arcade-building reconnection of the emerging magnetic arch with the ambient open field, with reconnection directly driven by the arch's emergence, but (3) none were unambiguously made by such emergence-driven reconnection. Thus, for these eight emerging BMRs, the observations indicate that emergence-driven external reconnection of the emerging magnetic arch with ambient open field at most produces a jet spire that is much fainter than in previously reported, much more obvious coronal jets driven by minifilament eruptions.
|
[
1504,
1981,
1483,
1503
] |
[
"solar magnetic reconnection",
"solar filament eruptions",
"solar corona",
"solar magnetic fields"
] |
2023AJ....166..134M
|
Lensing in the Blue. II. Estimating the Sensitivity of Stratospheric Balloons to Weak Gravitational Lensing
|
The Superpressure Balloon-borne Imaging Telescope (SUPERBIT) is a diffraction-limited, wide-field, 0.5 m, near-infrared to near-ultraviolet observatory designed to exploit the stratosphere's space-like conditions. SUPERBIT's 2023 science flight will deliver deep, blue imaging of galaxy clusters for gravitational lensing analysis. In preparation, we have developed a weak-lensing measurement pipeline with modern algorithms for PSF characterization, shape measurement, and shear calibration. We validate our pipeline and forecast SUPERBIT survey properties with simulated galaxy cluster observations in SUPERBIT's near-UV and blue bandpasses. We predict imaging depth, galaxy number (source) density, and redshift distribution for observations in SUPERBIT's three bluest filters; the effect of lensing sample selections is also considered. We find that, in three hours of on-sky integration, SUPERBIT can attain a depth of b = 26 mag and a total source density exceeding 40 galaxies per square arcminute. Even with the application of lensing-analysis catalog selections, we find b-band source densities between 25 and 30 galaxies per square arcminute with a median redshift of z = 1.1. Our analysis confirms SUPERBIT's capability for weak gravitational lensing measurements in the blue.
|
[
738,
584,
1797,
1858
] |
[
"high altitude balloons",
"galaxy clusters",
"weak gravitational lensing",
"astronomy data analysis"
] |
2020ApJS..247...10Z
|
Spectral Lines for Transition to Highly Excited States of Lithium in Magnetic Fields of White Dwarf Stars
|
We develop a two-dimensional B-spline approach in the cylindrical coordinate system to simulate spectra of lithium in magnetic fields of white dwarf stars. The advantage of the current approach is that it can be applied to calculate both low- and high-lying states, while the theoretical methods for describing magnetized lithium in the literature are limited to the treatment of the ground state and low-lying excited states. The magnetized atomic states are calculated with symmetries <SUP>2</SUP>0<SUP>+</SUP>, <SUP>2</SUP>0<SUP>-</SUP>, <SUP>2</SUP>-1<SUP>+</SUP>}, <SUP>2</SUP>(-1)<SUP>-</SUP>, <SUP>2</SUP>(-2)<SUP>+</SUP>, and the lowest 10 atomic states of each symmetry are involved. The magnetic field strengths stride a scope of field strengths of white dwarf stars. Atomic data of absorption spectra corresponding to transitions from the ground state or low-lying excited states to high-lying excited states are reported for magnetized lithium. These atomic data include energy levels, wavelengths, and oscillator strengths. Comparison is made between our results, and theoretical and experimental data reported in the literature. The current two-dimensional B-spline approach can systematically produce atomic data to model discrete atomic spectra of both low- and high-lying states of lithium in magnetic white dwarf stars.
|
[
2099
] |
[
"atomic spectroscopy"
] |
2021PSJ.....2...13G
|
Chromium Isotopic Evidence for Mixing of NC and CC Reservoirs in Polymict Ureilites: Implications for Dynamical Models of the Early Solar System
|
Nucleosynthetic isotope anomalies show that the first few million years of solar system history were characterized by two distinct cosmochemical reservoirs, CC (carbonaceous chondrites and related differentiated meteorites) and NC (the terrestrial planets and all other groups of chondrites and differentiated meteorites), widely interpreted to correspond to the outer and inner solar system, respectively. At some point, however, bulk CC and NC materials became mixed, and several dynamical models offer explanations for how and when this occurred. We use xenoliths of CC materials in polymict ureilite (NC) breccias to test the applicability of such models. Polymict ureilites represent regolith on ureilitic asteroids but contain carbonaceous chondrite-like xenoliths. We present the first <SUP>54</SUP>Cr isotope data for such clasts, which, combined with oxygen and hydrogen isotopes, show that they are unique CC materials that became mixed with NC materials in these breccias. It has been suggested that such xenoliths were implanted into ureilites by outer solar system bodies migrating into the inner solar system during the gaseous disk phase ∼3-5 Myr after CAI, as in the "Grand Tack" model. However, combined textural, petrologic, and spectroscopic observations suggest that they were added to ureilitic regolith at ∼50-60 Myr after CAI, along with ordinary, enstatite, and Rumuruti-type chondrites, as a result of the breakup of multiple parent bodies in the asteroid belt at this time. This is consistent with models for an early instability of the giant planets. The C-type asteroids from which the xenoliths were derived were already present in inner solar system orbits.
|
[
421,
1038,
15,
779,
867
] |
[
"dynamical evolution",
"meteorites",
"achondrites",
"impact phenomena",
"isotopic abundances"
] |
2021AJ....161...66K
|
Refined Telluric Absorption Correction for Low-resolution Ground-based Spectroscopy: Resolution and Radial Velocity Effects in the O<SUB>2</SUB> A-band for Exoplanets and K I Emission Lines
|
Telluric correction of spectroscopic observations is either performed via standard stars that are observed close in time and airmass along with the science target, or recently growing in importance, by theoretical telluric absorption modeling. Both approaches work fine when the telluric lines are resolved, i.e., at a spectral resolving power larger than about 10,000, and it is sufficient to facilitate the detection of spectral features at lower resolution. However, a meaningful quantitative analysis also requires the reliable recovery of line strengths. Here, we show for the Fraunhofer A-band of molecular O<SUB>2</SUB> that the standard telluric correction approach fails in this at lower spectral resolutions, as an example for the general problem. Doppler-shift-dependent errors of the restored flux may arise, which can amount to more than 50% in extreme cases, depending on the line shapes of the target spectral features. Two applications are discussed: the recovery of the O<SUB>2</SUB> band in the reflected light of an Earth analog atmosphere, as facilitated potentially in the future using an orbiting starshade and a ground-based extremely large telescope; and the recovery of the intrinsic ratio of the K I lines in the post-nova V4332 Sgr tracing the optical depth of the emitting region, to exemplify the relevance using present-day instrumentation. We show how one should derive correction functions for the compensation of the error in dependence of radial velocity shift, spectral resolution, and target line-profile function by use of high-resolution atmospheric transmission modeling, which has to be solved for the individual case.
|
[
113,
1558,
1858,
487,
437,
114
] |
[
"atmospheric effects",
"spectroscopy",
"astronomy data analysis",
"exoplanet atmospheres",
"earth atmosphere",
"atmospheric extinction"
] |
2024ApJ...961..119F
|
KilonovAE: Exploring Kilonova Spectral Features with Autoencoders
|
Kilonovae are likely a key site of heavy r-process element production in the Universe, and their optical/infrared spectra contain insights into both the properties of the ejecta and the conditions of the r-process. However, the event GW170817/AT2017gfo is the only kilonova so far with well-observed spectra. To understand the diversity of absorption features that might be observed in future kilonovae spectra, we use the TARDIS Monte Carlo radiative transfer code to simulate a suite of optical spectra spanning a wide range of kilonova ejecta properties and r-process abundance patterns. To identify the most common and prominent absorption lines, we perform dimensionality reduction using an autoencoder, and we find spectra clusters in the latent space representation using a Bayesian Gaussian Mixture model. Our synthetic kilonovae spectra commonly display strong absorption by strontium <SUB>38</SUB>Sr II, yttrium <SUB>38</SUB>Y II, and zirconium <SUB>40</SUB>Zr I-II, with strong lanthanide contributions at low electron fractions (Y <SUB>e</SUB> ≲ 0.25). When a new kilonova is observed, our machine-learning framework will provide context on the dominant absorption lines and key ejecta properties, helping to determine where this event falls within the larger "zoo" of kilonovae spectra.
|
[
1108,
1324,
1967,
2073,
1943
] |
[
"neutron stars",
"r-process",
"radiative transfer simulations",
"spectral line identification",
"dimensionality reduction"
] |
2024ApJ...962...28L
|
Multiple Shells Driven by Disk Winds: ALMA Observations in the HH 30 Outflow
|
We present archival Atacama Large Millimeter/submillimeter Array band 6 observations of the <SUP>13</SUP>CO (J = 2–1) and <SUP>12</SUP>CO (J = 2–1) molecular line emission of the protostellar system associated with HH 30. The <SUP>13</SUP>CO molecular line shows the accretion disk while the molecular outflow is traced by the emission of the <SUP>12</SUP>CO molecular line. We estimated a dynamical mass for the central object of 0.45 ± 0.14 M <SUB>⊙</SUB>, and a mass for the molecular outflow of (1.83 ± 0.19) × 10<SUP>‑4</SUP> M <SUB>⊙</SUB>. The molecular outflow presents an internal cavity as well as multiple outflowing shell structures. We distinguish three different shells with constant expansion (∼4–6 km s<SUP>‑1</SUP>) and possible rotation signatures (≤0.5 km s<SUP>‑1</SUP>). We find that the shells can be explained by magnetocentrifugal disk winds with launching radii R <SUB>launch</SUB> ≲ 4 au and a small magnetic lever arm λ ∼ 1.6–1.9. The multiple shell structure may be the result of episodic ejections of the material from the accretion disk associated with three different epochs with dynamical ages of 497 ± 15 yr, 310 ± 9 yr, and 262 ± 11 yr for the first, second, and third shells, respectively. The outermost shell was ejected 187 ± 17 yr before the middle shell, while the middle shell was launched 48 ± 14 yr before the innermost shell. Our estimations of the linear and angular momentum rates of the outflow as well as the accretion luminosity are consistent with the values expected if the outflow of HH 30 is produced by a wide-angle disk wind.
|
[
14,
722,
1569,
1636,
1834
] |
[
"accretion",
"herbig-haro objects",
"star formation",
"stellar winds",
"young stellar objects"
] |
2021ApJ...918L...1S
|
The Missing Link? Discovery of Pulsations in the Nitrogen-rich PG 1159 Star PG 1144+005
|
Up to 98% of all single stars will eventually become white dwarfs-stars that link the history and future evolution of the Galaxy, and whose previous evolution is engraved in their interiors. Those interiors can be studied using asteroseismology, utilizing stellar pulsations as seismic waves. The pulsational instability strips of DA and DB white dwarf stars are pure, allowing for the important generalization that their interior structure represents that of all DA and DB white dwarfs. This is not the case for the hottest pulsating white dwarfs, the GW Vir stars: only about 50% of white dwarfs in this domain pulsate. Several explanations for the impurity of the GW Vir instability strip have been proposed, based on different elemental abundances, metallicity, and helium content. Surprisingly, there is a dichotomy that only stars rich in nitrogen, which by itself cannot cause pulsation driving, pulsate-the only previous exception being the nitrogen-rich nonpulsator PG 1144+005. Here, we report the discovery of pulsations in PG 1144+005 based on new observations. We identified four frequency regions: 40, 55, 97, and 112 day<SUP>-1</SUP> with low and variable amplitudes of about 3-6 mmag and therefore confirm the nitrogen dichotomy. As nitrogen is a trace element revealing the previous occurrence of a very late thermal pulse (VLTP) in hot white dwarf stars, we speculate that it is this VLTP that provides the interior structure required to make a GW Vir pulsator.
|
[
1216,
1307,
1625,
1117,
1599
] |
[
"pg 1159 stars",
"pulsating variable stars",
"stellar pulsations",
"non-radial pulsations",
"stellar evolution"
] |
2022ApJ...927..238R
|
Global 3D Simulation of the Upper Atmosphere of HD189733b and Absorption in Metastable He I and Lyα Lines
|
A 3D fully self-consistent multifluid hydrodynamic aeronomy model is applied to simulate the hydrogen-helium expanding upper atmosphere of the hot Jupiter HD189733b, and related absorption in the Lyα line and the 10830 Å line of metastable helium. We studied the influence of a high-energy stellar flux, a stellar wind, and Lyα cooling to reproduce the available observations. We found that to fit the width of the absorption profile of the 10830 Å line the escaping upper atmosphere of the planet should be close to the energy-limited escape achieved with significantly reduced Lyα cooling at the altitudes with an H I density higher than 3 × 10<SUP>6</SUP> cm<SUP>-3</SUP>. Based on the performed simulations, we constrain the helium abundance in the upper atmosphere of HD189733b to be a rather low value of He/H ~ 0.005. We show that under the conditions of a moderate stellar wind similar to that of the Sun the absorption of the Lyα line takes place mostly within the Roche lobe due to thermal broadening at a level of about 7%. For an order of magnitude stronger wind, a significant absorption of about 15% at high blueshifted velocities of up to 100 km s<SUP>-1</SUP> is generated in the bowshock region, due to Doppler broadening. These blueshifted velocities are still lower than those (~200 km s<SUP>-1</SUP>) detected in one of the observations. We explain the differences between the performed observations, though not in all of the details, by stellar activity and the related fluctuations of the ionizing radiation (in the case of the 10830 Å line), and the stellar wind (in the case of the Lyα line).
|
[
487,
2021
] |
[
"exoplanet atmospheres",
"exoplanet atmospheric composition"
] |
2020ApJ...895...69B
|
Milky Way Subsystems from Globular Cluster Kinematics Using Gaia DR2 and HST Data
|
We employ Gaia DR2 proper motions for 151 Milky Way globular clusters (GCs) from Vasiliev in tandem with distances and line-of-sight velocities to derive their kinematical properties. To assign clusters to the Milky Way thick disk, bulge, and halo, we follow the approach of Posti et al., who distinguished among different Galactic stellar components using stars' orbits. In particular, we use the ratio L<SUB>z</SUB>/e, the Z projection of the angular momentum to the eccentricity, as a population tracer, which we complement with chemical abundances extracted from the literature and Monte Carlo simulations. We find that 20 GCs belong to the bar/bulge of the Milky Way, 35 exhibit disk properties, and 96 are members of the halo. Moreover, we find that halo GCs have close to zero rotational velocity with an average value $\langle {\rm{\Theta }}\rangle =1\pm 4$ km s<SUP>-1</SUP>. On the other hand, the sample of clusters that belong to the thick disk possess a significant rotation with average rotational velocity 179 ± 6 km s<SUP>-1</SUP>. The 20 GCs orbiting within the bar/bulge region of the Milky Way have an average rotational velocity of 49 ± 11 km s<SUP>-1</SUP>.
|
[
1054,
656,
1051,
1059
] |
[
"milky way galaxy",
"globular star clusters",
"milky way dynamics",
"milky way rotation"
] |
2020ApJS..246...67M
|
Cross Helicity Reversals in Magnetic Switchbacks
|
We consider 2D joint distributions of normalized residual energy, σ<SUB>r</SUB>(s, t), and cross helicity, σ<SUB>c</SUB>(s, t), during one day of Parker Solar Probe's (PSP's) first encounter as a function of wavelet scale s. The broad features of the distributions are similar to previous observations made by Helios in slow solar wind, namely well-correlated and fairly Alfvénic wind, except for a population with negative cross helicity that is seen at shorter wavelet scales. We show that this population is due to the presence of magnetic switchbacks, or brief periods where the magnetic field polarity reverses. Such switchbacks have been observed before, both in Helios data and in Ulysses data in the polar solar wind. Their abundance and short timescales as seen by PSP in its first encounter is a new observation, and their precise origin is still unknown. By analyzing these MHD invariants as a function of the wavelet scale, we show that magnetohydrodynamic (MHD) waves do indeed follow the local mean magnetic field through switchbacks, with a net Elsässer flux propagating inward during the field reversal and that they, therefore, must be local kinks in the magnetic field and not due to small regions of opposite polarity on the surface of the Sun. Such observations are important to keep in mind as computing cross helicity without taking into account the effect of switchbacks may result in spurious underestimation of σ<SUB>c</SUB> as PSP gets closer to the Sun in later orbits.
|
[
711,
830,
1544,
23
] |
[
"heliosphere",
"interplanetary turbulence",
"space plasmas",
"alfven waves"
] |
2020AJ....160..117R
|
The First Habitable-zone Earth-sized Planet from TESS. II. Spitzer Confirms TOI-700 d
|
We present Spitzer 4.5 μm observations of the transit of TOI-700 d, a habitable-zone Earth-sized planet in a multiplanet system transiting a nearby M-dwarf star (TIC 150428135, 2MASS J06282325-6534456). TOI-700 d has a radius of ${1.144}_{-0.061}^{+0.062}{R}_{\oplus }$ and orbits within its host star's conservative habitable zone with a period of 37.42 days (T<SUB>eq</SUB> ∼ 269 K). TOI-700 also hosts two small inner planets (R<SUB>b</SUB> = ${1.037}_{-0.064}^{+0.065}{R}_{\oplus }$ and R<SUB>c</SUB> = ${2.65}_{-0.15}^{+0.16}{R}_{\oplus }$ ) with periods of 9.98 and 16.05 days, respectively. Our Spitzer observations confirm the Transiting Exoplanet Survey Satellite (TESS) detection of TOI-700 d and remove any remaining doubt that it is a genuine planet. We analyze the Spitzer light curve combined with the 11 sectors of TESS observations and a transit of TOI-700 c from the LCOGT network to determine the full system parameters. Although studying the atmosphere of TOI-700 d is not likely feasible with upcoming facilities, it may be possible to measure the mass of TOI-700 d using state-of-the-art radial velocity (RV) instruments (expected RV semiamplitude of ∼70 cm s<SUP>-1</SUP>).
|
[
498,
695,
696,
2050,
47,
486,
489,
484
] |
[
"exoplanets",
"habitable planets",
"habitable zone",
"low mass stars",
"antarctic observatories",
"exoplanet astronomy",
"exoplanet detection methods",
"exoplanet systems"
] |
2022ApJ...941..112B
|
Electron Density Variations in the Interstellar Medium and the Average Frequency Profile of a Scintle from Pulsar Scintillation Spectra
|
We observed the scintillation pattern of nine bright pulsars at 324 MHz and three at 1.68 GHz and analyzed the wavenumber spectrum, which is related to electron density variations of the plasma turbulence of the interstellar medium (ISM). For all pulsars the frequency section of the autocorrelation function (ACF) of the dynamic spectra to at least 45% of the maximum corresponds to predictions of scattering theories with a range of power-law exponents of the wavenumber spectrum of 3.56 ≤ α ≤ 3.97 with errors ≤0.05 and a mean with standard deviation of 3.76 ± 0.13. The range includes α = 3.67 for the Kolmogorov spectrum. Similar results, although with larger errors, were found from the Fourier transform of the ACFs down to ~10<SUP>-3</SUP> of the maximum. No clear case of a distinction between thin-screen and extended-medium scattering models was found. The average frequency profile of the scintles can be characterized for steep wavenumber spectra with α ≲ 4 by a cusp with a somewhat rounded peak. For flatter spectra, down to at least α ~ 3.56 the cusp with its peak becomes more pronounced and its decay steepens. We discuss our findings in the context of the scattering characteristics of the ISM.
|
[
855,
1353,
1769,
854
] |
[
"interstellar scintillation",
"radio pulsars",
"very long baseline interferometry",
"interstellar scattering"
] |
2022ApJ...931L..24C
|
Radiative Transfer Modeling of Chang'e-4 Spectroscopic Observations and Interpretation of the South Pole-Aitken Compositional Anomaly
|
Chang'e-4 landed in the Von Kármán basaltic zone affected by Finsen ejecta from the South Pole-Aitken (SPA) "compositional anomaly" (SPACA), providing an opportunity to untangle the origin of the SPACA. We developed a mineral abundance unmixing model and built a spectral library composed of mineral mixtures of plagioclase, low-Ca pyroxene, high-Ca pyroxene, and olivine. Based on the mineral abundances returned by our model, the average plagioclase abundance (60.4 vol.%) of SPACA is beyond the high-plagioclase end of the mineralogical range of SPA impact melt differentiation products and would require an additional contribution from crustal materials. We suggest that either the crust was not entirely removed in the SPA-forming impact or the ejecta from post-SPA basins fed feldspathic materials back onto the SPA basin floor. Our unmixing analyses indicate that the surface regolith of the SPACA is a mixture of 70.2% crustal materials and 29.8% Fe- and incompatible-element-enriched materials.
|
[
1692,
948,
952,
962,
969,
974,
972
] |
[
"the moon",
"lunar composition",
"lunar evolution",
"lunar mineralogy",
"lunar probes",
"lunar surface",
"lunar science"
] |
2021ApJS..254...31C
|
Stellar Metallicities from SkyMapper Photometry. II. Precise Photometric Metallicities of ∼280,000 Giant Stars with [Fe/H] < -0.75 in the Milky Way
|
The Milky Way's metal-poor stars are nearby ancient objects that are used to study early chemical evolution and the assembly and structure of the Milky Way. Here we present reliable metallicities of ∼280,000 stars with -3.75 ≲ [Fe/H] ≲ -0.75 down to g = 17 derived using metallicity-sensitive photometry from the second data release of the SkyMapper Southern Survey. We use the dependency of the flux through the SkyMapper v filter on the strength of the Ca II K absorption features, in tandem with SkyMapper u, g, i photometry, to derive photometric metallicities for these stars. We find that metallicities derived in this way compare well to metallicities derived in large-scale spectroscopic surveys, and we use such comparisons to calibrate and quantify systematics as a function of location, reddening, and color. We find good agreement with metallicities from the APOGEE, LAMOST, and GALAH surveys, based on a standard deviation of σ ∼ 0.25 dex of the residuals of our photometric metallicities with respect to metallicities from those surveys. We also compare our derived photometric metallicities to metallicities presented in a number of high-resolution spectroscopic studies to validate the low-metallicity end ([Fe/H] < -2.5) of our photometric metallicity determinations. In such comparisons, we find the metallicities of stars with photometric [Fe/H] < -2.5 in our catalog show no significant offset and a scatter of σ ∼ 0.31 dex level relative to those in high-resolution work when considering the cooler stars (g - i > 0.65) in our sample. We also present an expanded catalog containing photometric metallicities of ∼720,000 stars as a data table for further exploration of the metal-poor Milky Way.
|
[
1284,
1054
] |
[
"population ii stars",
"milky way galaxy"
] |
2024ApJ...968...35R
|
Escape Velocity Mass of A1063
|
We measure the radius–velocity phase-space edge profile of A1063 using galaxy redshifts from Karman et al. and Mercurio et al. Combined with a cosmological model and after accounting for interlopers and sampling effects, we infer the escape velocity profile. Using the Poisson equation, we then directly constrain the gravitational potential profile and find excellent agreement between three different density models. For the Navarro–Frenk–White profile, we find log<SUB>10</SUB>(M <SUB>200,crit</SUB>) = M <SUB>⊙</SUB>, consistent to within 1σ of six recently published lensing masses. We argue that this consistency is due to the fact that the escape technique shares no common systematics with lensing other than radial binning. These masses are 2–4σ lower than estimates made using X-ray data, in addition to the Gómezet al. velocity dispersion estimate. We measure the 1D velocity dispersion within r <SUB>200</SUB> to be km s<SUP>‑1</SUP>, which combined with our escape velocity mass, brings the dispersion for A1063 in-line with hydrodynamic cosmological simulations for the first time.
|
[
343,
584,
670,
351
] |
[
"cosmology",
"galaxy clusters",
"gravitational lensing",
"dark energy"
] |
2022ApJ...935L..35F
|
The Planetary Nebula in the 500 Myr Old Open Cluster M37
|
We report confirmation of a large, evolved, bipolar planetary nebula and its blue, white dwarf central star as a member of the ~500 Myr old Galactic open star cluster M37 (NGC 2099). This is only the third known example of a planetary nebula in a Galactic open cluster and was found via our ongoing program of identifying and studying planetary nebulae-open cluster associations. High confidence in the association comes from the consistent radial velocities and proper motions for the confirmed central star and cluster stars from Gaia, reddening agreement, and location of the planetary nebula well within the tidal cluster boundary. Interestingly, all three Galactic examples have bipolar morphology and likely Type-I chemistry, both characteristics of higher mass progenitors. In this case the progenitor star mass is in the midrange of ~2.8 M <SUB>☉</SUB>. It provides a valuable, additional point on the key stellar initial-to-final mass relation independent of cluster white dwarf estimates and also falls in a gap in the poorly sampled mass region. This planetary nebula also appears to have the largest kinematical age ever determined and implies increased visibility lifetimes when they are located in clusters.
|
[
1160,
1249
] |
[
"open star clusters",
"planetary nebulae"
] |
2021PSJ.....2..191C
|
FOSSIL. I. The Spin Rate Limit of Jupiter Trojans
|
Rotation periods of 53 small (diameters 2 km < D < 40 km) Jupiter Trojans (JTs) were derived using the high-cadence lightcurves obtained by the FOSSIL phase I survey, a Subaru/Hyper Suprime-Cam intensive program. These are the first reported periods measured for JTs with D < 10 km. We found a lower limit of the rotation period near 4 hr, instead of the previously published result of 5 hr found for larger JTs. Assuming a rubble-pile structure for JTs, a bulk density of ≈0.9 g cm<SUP>-3</SUP> is required to withstand this spin rate limit, consistent with the value ~0.8-1.0 g cm<SUP>-3</SUP> derived from the binary JT system, (617) Patroclus-Menoetius system.
|
[
874,
2211,
1916,
2109
] |
[
"jupiter trojans",
"asteroid rotation",
"time series analysis",
"time domain astronomy"
] |
2023ApJ...956...66Z
|
Regulation of Proton-α Differential Flow by Compressive Fluctuations and Ion-scale Instabilities in the Solar Wind
|
Large-scale compressive slow-mode-like fluctuations can cause variations in the density, temperature, and magnetic-field magnitude in the solar wind. In addition, they also lead to fluctuations in the differential flow U <SUB>pα </SUB> between α-particles and protons (p), which is a common source of free energy for the driving of ion-scale instabilities. If the amplitude of the compressive fluctuations is sufficiently large, the fluctuating U <SUB>pα </SUB> intermittently drives the plasma across the instability threshold, leading to the excitation of ion-scale instabilities and thus the growth of corresponding ion-scale waves. The unstable waves scatter particles and reduce the average value of U <SUB>pα </SUB>. We propose that this "fluctuating-drift effect" maintains the average value of U <SUB>pα </SUB> well below the marginal instability threshold. We model the large-scale compressive fluctuations in the solar wind as long-wavelength slow-mode waves using a multi-fluid model. We numerically quantify the fluctuating-drift effect for the Alfvén/ion-cyclotron and fast-magnetosonic/whistler instabilities. We show that measurements of the proton-α differential flow and compressive fluctuations from the Wind spacecraft are consistent with our predictions for the fluctuating-drift effect. This effect creates a new channel for a direct cross-scale energy transfer from large-scale compressions to ion-scale fluctuations.
|
[
711,
1534,
1544
] |
[
"heliosphere",
"solar wind",
"space plasmas"
] |
2021ApJ...911...70B
|
Near-infrared Coronal Line Observations of Dwarf Galaxies Hosting AGN-driven Outflows
|
We have obtained Keck near-infrared spectroscopy of a sample of nine M<SUB>⋆</SUB> < 10<SUP>10</SUP> M<SUB>⊙</SUB> dwarf galaxies to confirm active galactic nuclei (AGNs) activity and the presence of galaxy-wide, AGN-driven outflows through coronal line (CL) emission. We find strong CL detections in 5/9 galaxies (55%) with line ratios incompatible with shocks, confirming the presence of AGNs in these galaxies. Similar CL detection rates are found in larger samples of more massive galaxies hosting type 1 and 2 AGNs. We investigate the connection between the CLs and galaxy-wide outflows by analyzing the kinematics of the CL region as well as the scaling of gas velocity with ionization potential of different CLs. In addition, using complementary Keck Cosmic Web Imager observations of these objects, we find that the outflow velocities measured in [Si VI] are generally faster than those seen in [O III]. The galaxies with the fastest outflows seen in [O III] also have the highest [Si VI] luminosity. The lack of J-band CN absorption features, which are often associated with younger stellar populations, provides further evidence that these outflows are driven by AGNs in low-mass galaxies.
|
[
16,
2017,
416,
1447,
1093,
17,
594
] |
[
"active galactic nuclei",
"agn host galaxies",
"dwarf galaxies",
"seyfert galaxies",
"near infrared astronomy",
"active galaxies",
"galaxy evolution"
] |
2021ApJ...910...17P
|
Orbital Torus Imaging: Using Element Abundances to Map Orbits and Mass in the Milky Way
|
Many approaches to galaxy dynamics assume that the gravitational potential is simple and the distribution function is time invariant. Under these assumptions there are traditional tools for inferring potential parameters given observations of stellar kinematics (e.g., Jeans models). However, spectroscopic surveys measure many stellar properties beyond kinematics. Here we present a new approach for dynamical inference, Orbital Torus Imaging, which makes use of kinematic measurements and element abundances (or other invariant labels). We exploit the fact that, in steady state, stellar labels vary systematically with orbit characteristics (actions), yet must be invariant with respect to orbital phases (conjugate angles). The orbital foliation of phase space must therefore coincide with surfaces along which all moments of all stellar label distributions are constant. Both classical-statistics and Bayesian methods can be built on this; these methods will be more robust and require fewer assumptions than traditional tools because they require no knowledge of the (spatial) survey selection function and do not involve second moments of velocity distributions. We perform a classical-statistics demonstration with red giant branch stars from the APOGEE surveys: we model the vertical orbit structure in the Milky Way disk to constrain the local disk mass, scale height, and the disk-halo mass ratio (at fixed local circular velocity). We find that the disk mass can be constrained (naïvely) at the few-percent level with Orbital Torus Imaging using only eight element-abundance ratios, demonstrating the promise of combining stellar labels with dynamical invariants.
|
[
591,
1051,
1608,
1882,
224,
1558
] |
[
"galaxy dynamics",
"milky way dynamics",
"stellar kinematics",
"astrostatistics",
"chemical abundances",
"spectroscopy"
] |
2021ApJ...917...16C
|
Anomalous Intensities in the Infrared Emission of CH<SUP>+</SUP> Explained by Quantum Nuclear Motion and Electric Dipole Calculations
|
The unusual infrared emission patterns of CH<SUP>+</SUP>, recently detected in the planetary nebula NGC 7027, are examined theoretically with high-accuracy rovibrational wavefunctions and ab initio dipole moment curves. The calculated transition dipole moments quantitatively reproduce the observed J-dependent intensity variation, which is ascribed to underlying centrifugal distortion-induced interference effects. We discuss the implications of this anomalous behavior for astrochemical modeling of CH<SUP>+</SUP> production and excitation, and provide a simple expression to estimate the magnitude of this effect for other light diatomic molecules with small dipole derivatives.
|
[
2095,
2084,
2074
] |
[
"molecular spectroscopy",
"line intensities",
"transition probabilities"
] |
2021ApJ...907...87L
|
The Evolution of a Newborn Millisecond Magnetar with a Propeller-recycling Disk
|
A rapidly rotating and highly magnetized neutron star (NS) could be formed from explosive phenomena such as superluminous supernovae and gamma-ray bursts. This newborn NS can substantially influence the emission of these explosive transients through its spin-down. The spin-down evolution of the NS can sometimes be affected by fallback accretion, although it is usually regulated by the magnetic dipole radiation and gravitational wave radiation of the NS. Under appropriate conditions, the accreting material can be first ejected and subsequently recycled back, so that the accretion disk can remain in a quasi-steady state for a long time. Here we describe the interaction of the NS with such a propeller-recycling disk and their coevolution. Our result shows that the spin-down of the NS can be initially dominated by the propeller, which prevents the disk material from falling onto the NS until hundreds or thousands of seconds later. It is suggested that the abrupt fall of the disk material onto the NS could significantly suppress the magnetic dipole radiation and then convert the NS from a normal magnetar to a low-field magnetar. This evolution behavior of the newborn NS can help us understand the very different influence of the NS on the early GRB afterglows and the late supernova/kilonova emission.
|
[
1108,
992,
1579,
629
] |
[
"neutron stars",
"magnetars",
"stellar accretion disks",
"gamma-ray bursts"
] |
2021ApJ...914...75R
|
Eccentricity without Measuring Eccentricity: Discriminating among Stellar Mass Black Hole Binary Formation Channels
|
We show how the observable number of binaries in LISA is affected by eccentricity through its influence on the peak gravitational-wave frequency, enhanced binary number density required to produce the LIGO observed rate, and the reduced signal-to-noise ratio (S/N) for an eccentric event. We also demonstrate how these effects should make it possible to learn about the eccentricity distribution and formation channels by counting the number of binaries as a function of frequency, even with no explicit detection of eccentricity. We also provide a simplified calculation for S/N of eccentric binaries.
|
[
675
] |
[
"gravitational wave astronomy"
] |
2022ApJS..262....8P
|
Mining S-PLUS for Metal-poor Stars in the Milky Way
|
This work presents the medium-resolution (R ~ 1500) spectroscopic follow-up of 522 low-metallicity star candidates from the Southern Photometric Local Universe Survey (S-PLUS). The objects were selected from narrowband photometry, taking advantage of the metallicity-sensitive S-PLUS colors. The follow-up observations were conducted with the Blanco and Gemini South telescopes, using the COSMOS and GMOS spectrographs, respectively. The stellar atmospheric parameters (T <SUB>eff</SUB>, $\mathrm{log}\,g$ , and [Fe/H]), as well as carbon and α-element abundances, were calculated for the program stars in order to assess the efficacy of the color selection. Results show that ${92}_{-3}^{+2} \% $ of the observed stars have [Fe/H] ≤ -1.0, ${83}_{-3}^{+3} \% $ have [Fe/H] ≤ -2.0, and ${15}_{-3}^{+3} \% $ have [Fe/H] ≤ -3.0, including two ultra metal-poor stars ([Fe/H] ≤ -4.0). The 80th percentile for the metallicity cumulative distribution function of the observed sample is [Fe/H] = -2.04. The sample also includes 68 carbon-enhanced metal-poor stars. Based on the calculated metallicities, further S-PLUS color cuts are proposed, which can increase the fractions of stars with [Fe/H] ≤ -1.0 and ≤ -2.0 to 98% and 88%, respectively. Such high success rates enable targeted high-resolution spectroscopic follow-up efforts, as well as provide selection criteria for fiber-fed multiplex spectroscopic surveys.
|
[
1088,
1031,
1584,
224
] |
[
"narrow band photometry",
"metallicity",
"stellar atmospheres",
"chemical abundances"
] |
2020ApJ...893L..46Z
|
Dynamic Kink Instability and Transverse Motions of Solar Spicules
|
Hydrodynamic jets are unstable to the kink instability (m = 1 mode in cylindrical geometry) owing to the centripetal force, which increases the transverse displacement of the jet. When the jet moves along a magnetic field, the Lorentz force tries to decrease the displacement and stabilize the instability of sub-Alfvénic flows. The threshold of the instability depends on the Alfvén Mach number (the ratio of Alfvén and jet speeds). We suggest that the dynamic kink instability may be important to explain observed transverse motions of type II spicules in the solar atmosphere. We show that the instability may begin for spicules that rise up at the peripheries of vertically expanding magnetic flux tubes because of the decrease of the Alfvén speed in both the vertical and the radial directions. Therefore, inclined spicules may be more unstable and have higher transverse speeds. Periods and growth times of unstable modes in the conditions of type II spicules have values of 30 s and 25-100 s, respectively, which are comparable to the lifetime of the structures. This may indicate an interconnection between high-speed flow and the rapid disappearance of type II spicules in chromospheric spectral lines.
|
[
1525,
1479,
1074
] |
[
"solar spicules",
"solar chromosphere",
"solar mottles"
] |
2021ApJ...908....5B
|
On the Rigidity Spectrum of Cosmic-Ray Variations within Propagating Interplanetary Disturbances: Neutron Monitor and SOHO/EPHIN Observations at ∼1-10 GV
|
The rigidity dependence of all Forbush decreases (FDs) recorded from 1995 to 2015 has been determined using neutron monitor (NM) and Solar and Heliospheric Observatory (SOHO) (EPHIN) spacecraft data, covering the energy (rigidity) range from ∼433 MeV (1 GV) to 9.10 GeV (10 GV). We analyzed a total of 421 events and determined the spectrum in rigidity with an inverse power-law fit. As a result, the mean spectral index was identified to be ⟨γ<SUB>F</SUB>⟩ = 0.46 ± 0.02. The majority (∼66%) of the FDs have γ<SUB>F</SUB> within the range 0.3-0.7. The remaining one-third of the events (∼33%) have either (very) soft or hard FD spectra, with the latter being more common than the former. Significant variations of γ<SUB>F</SUB> occur within almost every FD event. During the initial FD decay phase the spectrum becomes gradually harder, in contrast to the recovery phase, when it becomes softer. Additionally, low energies (rigidities) seem to be better suited for studying the fine structure of interplanetary disturbances (primarily interplanetary coronal mass ejections) that lead to FDs. In particular, FDs recorded by the EPHIN instrument on SOHO better capture a two-step structure than FDs observed by NMs. Finally, the ejecta of an ICME, especially when identified as a magnetic cloud, often leads to abrupt changes in the slope of γ<SUB>F</SUB>.
|
[
310,
546,
314
] |
[
"solar coronal mass ejections",
"forbush effect",
"corotating streams"
] |
2021ApJ...909..189K
|
Scalaron Gravity near Sagittarius A*: Investigation of Spin of the Black Hole and Observing Requirements
|
In this paper the author applies the scalaron gravity field and corresponding Yukawa coupling (derived by Kalita from the consideration of quantum vacuum fluctuations with UV and IR scales) to examine the scales of stellar orbits near the Galactic Center black hole, which can be probed by upcoming astrometric facilities for constraining modified gravity. Through the assumption that the pericenter shift of stellar orbits becomes of the order of spin and quadrupole moment effects of the black hole, it is found that for semimajor axes bounded below by time scales of gravitational wave emission and stellar age and above by S-2 like orbits (a = 990 au) the black hole spin with 0.1 ≤ χ ≤ 0.980 is eligible to probe scalaron masses within (10<SUP>-22</SUP>-10<SUP>-18</SUP>) eV and also the scalaron coupling, α = 2.73 × 10<SUP>-4</SUP> derived earlier from quantum vacuum fluctuations. The orbital eccentricities are considered as e = 0.1, 0.5, and 0.9. Astrometric categories with σ = 10, 50, and 100 μas are used to probe the time scales and number of observing campaigns required for simultaneously constraining scalaron mass and black hole spin. It is found that extraction of black hole spin is possible within a = (74-433) au through 10 μas facilities. The present analysis is realized to be an independent opportunity to simultaneously constrain scalaron coupling, black hole spin, and tidal charge and hence to reveal the true nature of the spacetime structure of our nearest supermassive black hole.
|
[
159,
565
] |
[
"black hole physics",
"galactic center"
] |
2020ApJ...903..107K
|
An Analysis of Soft X-Ray Structures at Kiloparsec Distances from the Active Nucleus of Centaurus A Galaxy
|
Here we reanalyze the archival Chandra data for the central parts of the Centaurus A radio galaxy, aiming for a systematic investigation of the X-ray emission associated with the inner radio lobes in the system, and their immediate surroundings. In particular, we focus on four distinct features characterized by the soft excess with respect to the adjacent fields. Those include the two regions located at kiloparsec distances from the nucleus to the west and east, the extended bow-shock structure to the south, and a fragment of a thin arc north of the center. The selected north, west, and south features coincide with the edges of the radio lobes, while the east structure is seemingly displaced from the radio-emitting plasma. Our X-ray spectral analysis reveals (i) a power-law emission component with photon index Γ ∼ 2 in the north, east, and south regions, and (ii) a dense (number density ∼0.3 cm<SUP>-3</SUP>) and relatively cold (temperature ∼ 0.2 keV) gas in the east and west regions. The power-law emission is consistent with the synchrotron continuum generated at the edges of the radio structure, and implies that the efficiency of the electron acceleration at the terminal bow shock does not vary dramatically over the inner lobes' extension. The presence of gaseous condensations, on the other hand, could possibly be understood in terms of a massive outflow from the central regions of the galaxy.
|
[
739,
2035,
1119,
17,
1810,
1822
] |
[
"high energy astrophysics",
"x-ray active galactic nuclei",
"non-thermal radiation sources",
"active galaxies",
"x-ray astronomy",
"x-ray sources"
] |
2022ApJ...927...13Z
|
Metal-poor Stars Observed with the Southern African Large Telescope II. An Extended Sample
|
We present results from high-resolution (R ~ 40,000) spectroscopic observations of over 200 metal-poor stars, mostly selected from the RAVE survey, using the Southern African Large Telescope. We were able to derive stellar parameters for a total of 108 stars; an additional sample of 50 stars from this same effort was previously reported on by Rasmussen et al. Among our newly reported observations, we identify 84 very metal-poor (VMP; [Fe/H] < -2.0, 53 newly identified) stars and three extremely metal-poor (EMP; [Fe/H] < -3.0, one newly identified) stars. The elemental abundances were measured for carbon, as well as several other α-elements (Mg, Ca, Sc, and Ti), iron-peak elements (Mn, Co, Ni, and Zn), and neutron-capture elements (Sr, Ba, and Eu). Based on these measurements, the stars are classified by their carbon and neutron-capture abundances into carbon-enhanced metal-poor (CEMP; [C/Fe] > +0.70), CEMP subclasses, and by the level of their r-process abundances. A total of 17 are classified as CEMP stars. There are 11 CEMP-r stars (eight newly identified), one CEMP-s star (newly identified), two possible CEMP-i stars (one newly identified), and three CEMP-no stars (all newly identified) in this work. We found 11 stars (eight newly identified) that are strongly enhanced in r-process elements (r-II; [Eu/Fe] > +0.70), 38 stars (31 newly identified) that are moderately enhanced in r-process elements (r-I; +0.30 < [Eu/Fe] ≤ + 0.70), and one newly identified limited-r star.
|
[
1060,
1577,
1584,
2105,
1324,
1284
] |
[
"milky way stellar halo",
"stellar abundances",
"stellar atmospheres",
"cemp stars",
"r-process",
"population ii stars"
] |
2022ApJ...929...37W
|
Is There an Enormous Cold Front at the Virial Radius of the Perseus Cluster?
|
We present new XMM-Newton observations extending the mosaic of the Perseus cluster out to the virial radius to the west. Previous studies with ROSAT have reported a large excess in surface brightness to the west, possibly the result of large-scale gas sloshing. In our new XMM-Newton observations we have found two X-ray surface brightness edges at 1.2 and 1.7 Mpc to the west. The temperature measurements obtained with Suzaku data indicate that the temperature increases sharply at each edge, consistent with what would be expected from cold fronts. However the the XMM-Newton data are affected by stray light, which at present is a poorly understood source of systematic error that can also lead to curved features in X-ray images. To test our results, we compared our X-ray surface brightness profile with that obtained from ROSAT PSPC data. While the edge at 1.2 Mpc is confirmed by ROSAT PSPC, the ROSAT data quality is insufficient to confirm the outer edge at 1.7 Mpc. Further observations with future X-ray telescopes will be needed to confirm the existence of the outer edge at 1.7 Mpc. By comparing with numerical simulations, we find that these large cold fronts require a large impact parameter, and low-mass ratio mergers that can produce fast gas motions without destroying the cluster core.
|
[
584,
858,
1214,
1810,
739
] |
[
"galaxy clusters",
"intracluster medium",
"perseus cluster",
"x-ray astronomy",
"high energy astrophysics"
] |
2021ApJ...911...76X
|
Two X-Ray Plateaus of Gamma-Ray Bursts: Energy Injection from Nascent Magnetars with an Evolving Magnetic Inclination Angle
|
As the central engine of gamma-ray bursts (GRBs), a nascent magnetar can release its rotational energy by magnetic dipole radiation. This energy is injected into the outflow of the GRB jet. With the rapid evolution of the magnetic inclination angle, the perpendicular component of the magnetar's surface magnetic field decreases rapidly. The energy loss rate of the magnetar is characterized by two different timescales. This peculiar two-stage energy injection model will affect the shape of the X-ray afterglow light curve. It is shown that a new shallow decay phase will emerge following the initial shallow decay phase. As a result, there could be two plateaus in the X-ray light curve. The effects of various physical parameters on the light curves are studied in detail. It is found that the observed afterglows of GRB 161217A and GRB 190114A, both having two plateaus in the light curve, can be well fitted in our framework.
|
[
629,
992,
918
] |
[
"gamma-ray bursts",
"magnetars",
"light curves"
] |
2021ApJ...911..128K
|
Star Formation Efficiency and Dispersal of Giant Molecular Clouds with UV Radiation Feedback: Dependence on Gravitational Boundedness and Magnetic Fields
|
Molecular clouds are supported by turbulence and magnetic fields, but quantifying their influence on cloud life cycle and star formation efficiency (SFE) remains an open question. We perform radiation magnetohydrodynamic simulations of star-forming giant molecular clouds (GMCs) with UV radiation feedback, in which the propagation of UV radiation via ray tracing is coupled to hydrogen photochemistry. We consider 10 GMC models that vary in either initial virial parameter (1 ≤ α<SUB>vir,0</SUB> ≤ 5) or dimensionless mass-to-magnetic flux ratio (0.5 ≤ μ<SUB>Φ,0</SUB> ≤ 8 and ∞ ); the initial mass 10<SUP>5</SUP> M<SUB>⊙</SUB> and radius 20 pc are fixed. Each model is run with five different initial turbulence realizations. In most models, the duration of star formation and the timescale for molecular gas removal (primarily by photoevaporation) are 4-8 Myr. Both the final SFE (ɛ<SUB>*</SUB>) and time-averaged SFE per freefall time (ɛ<SUB>ff</SUB>) are reduced by strong turbulence and magnetic fields. The median ɛ<SUB>*</SUB> ranges between 2.1% and 9.5%. The median ɛ<SUB>ff</SUB> ranges between 1.0% and 8.0%, and anticorrelates with α<SUB>vir,0</SUB>, in qualitative agreement with previous analytic theory and simulations. However, the time-dependent α<SUB>vir</SUB>(t) and ɛ<SUB>ff,obs</SUB>(t) based on instantaneous gas properties and cluster luminosity are positively correlated due to rapid evolution, making observational validation of star formation theory difficult. Our median ɛ<SUB>ff,obs</SUB>(t) ≈ 2% is similar to observed values. We show that the traditional virial parameter estimates the true gravitational boundedness within a factor of 2 on average, but neglect of magnetic support and velocity anisotropy can sometimes produce large departures from traditional virial parameter estimates. Magnetically subcritical GMCs are unlikely to represent sites of massive star formation given their unrealistic columnar outflows, prolonged lifetime, and low escape fraction of radiation.
|
[
653,
694,
2009,
1569,
994,
1602,
847
] |
[
"giant molecular clouds",
"h ii regions",
"radiative magnetohydrodynamics",
"star formation",
"magnetic fields",
"stellar feedback",
"interstellar medium"
] |
2023ApJ...953..133K
|
A Three-dimensional Model for the Evolution of Magnetohydrodynamic Turbulence in the Outer Heliosphere
|
We present a time-dependent, three-dimensional single-fluid model for the transport of magnetohydrodynamic (MHD) turbulence that is self-consistently evolving with a dynamic large-scale solar wind in the outer heliosphere. The emphasis is on the region beyond the termination shock, where the solar wind expands subsonically, as well as sub-Alfvénically and nonradially. In extension of earlier work, we refine the treatment of turbulence by considering, in addition to the Elsässer energies, a nonconstant energy difference (or residual energy) and by allowing each of these quantities its own characteristic correlation length scale. While the nonlinear effects in the equations for the Elsässer energies and their length scales are implemented using familiar von Kármán-Howarth style modeling of homogeneous MHD turbulence, the energy difference, which is not conserved in the absence of dissipation, and its length scale are modeled using distinct approaches. We also clarify the impact of the choice of measurement direction for correlation functions associated with two-dimensional fluctuations in transport models. Finally, we illustrate and study the solutions of the resulting six-equation model in detail.
|
[
710,
830,
1535
] |
[
"heliosheath",
"interplanetary turbulence",
"solar wind termination"
] |
2022ApJ...937...66P
|
Deconfusing Detections in Directly Imaged Multiplanet Systems
|
High-contrast images from future space-based telescopes may contain several planets from multiplanet systems and potentially a few planet-like speckles. When taken several months apart, the short-period planets and speckles will appear to move significantly, to the point that it might not be clear which point source (detection) in the image belongs to which object. In this work, we develop a tool, the deconfuser, to test quickly all the plausible partitions of detections by planets based on orbital mechanics. We then apply the deconfuser to a large set of simulated observations to estimate "confusion" rates, i.e., how often there are multiple distinct orbit combinations that describe the data well. We find that in the absence of missed and false detections, four observations are sufficient to avoid confusion, except for systems with high inclinations (above 75°). In future work, the deconfuser will be integrated into mission simulation tools, such as EXOSIMS, to assess the risk of confusion in missions such as the IR/O/UV large telescope recommended by the Astro2020 decadal survey. <SUP>*</SUP> Submitted on April, 1st, 2022
|
[
2130,
1175,
313,
1914
] |
[
"astrometric exoplanet detection",
"orbit determination",
"coronagraphic imaging",
"regression"
] |
2021ApJ...911..109S
|
Identifying RR Lyrae Variable Stars in Six Years of the Dark Energy Survey
|
We present a search for RR Lyrae stars using the full six-year data set from the Dark Energy Survey covering ∼5000 deg<SUP>2</SUP> of the southern sky. Using a multistage multivariate classification and light-curve template-fitting scheme, we identify RR Lyrae candidates with a median of 35 observations per candidate. We detect 6971 RR Lyrae candidates out to ∼335 kpc, and we estimate that our sample is >70% complete at ∼150 kpc. We find excellent agreement with other wide-area RR Lyrae catalogs and RR Lyrae studies targeting the Magellanic Clouds and other Milky Way satellite galaxies. We fit the smooth stellar halo density profile using a broken-power-law model with fixed halo flattening (q = 0.7), and we find strong evidence for a break at ${R}_{0}={32.1}_{-0.9}^{+1.1}\,\mathrm{kpc}$ with an inner slope of ${n}_{1}=-{2.54}_{-0.09}^{+0.09}$ and an outer slope of ${n}_{2}=-{5.42}_{-0.14}^{+0.13}$ . We use our catalog to perform a search for Milky Way satellite galaxies with large sizes and low luminosities. Using a set of simulated satellite galaxies, we find that our RR Lyrae-based search is more sensitive than those using resolved stellar populations in the regime of large (r<SUB>h</SUB> ≳ 500 pc), low-surface-brightness dwarf galaxies. A blind search for large, diffuse satellites yields three candidate substructures. The first can be confidently associated with the dwarf galaxy Eridanus II. The second has a distance and proper motion similar to the ultrafaint dwarf galaxy Tucana II but is separated by ∼5 deg. The third is close in projection to the globular cluster NGC 1851 but is ∼10 kpc more distant and appears to differ in proper motion.
|
[
1410,
1413,
1060
] |
[
"rr lyrae variable stars",
"rrab variable stars",
"milky way stellar halo"
] |
2023ApJ...952L..41K
|
Disk Galaxies Are Self-similar: The Universality of the H I-to-Halo Mass Ratio for Isolated Disks
|
Observed scaling relations in galaxies between baryons and dark matter global properties are key to shed light on the process of galaxy formation and on the nature of dark matter. Here, we study the scaling relation between the neutral hydrogen (H I) and dark matter mass in isolated rotationally supported disk galaxies at low redshift. We first show that state-of-the-art galaxy formation simulations predict that the H I-to-dark-halo mass ratio decreases with stellar mass for the most massive disk galaxies. We then infer dark matter halo masses from high-quality rotation curve data for isolated disk galaxies in the local Universe and report on the actual universality of the H I-to-dark halo mass ratio for these observed galaxies. This scaling relation holds for disks spanning a range of 4 orders of magnitude in stellar mass and 3 orders of magnitude in surface brightness. Accounting for the diversity of rotation curve shapes in our observational fits decreases the scatter of the H I-to-dark halo mass ratio while keeping it constant. This finding extends the previously reported discrepancy for the stellar-to-halo mass relation of massive disk galaxies within galaxy formation simulations to the realm of neutral atomic gas. Our result reveals that isolated galaxies with regularly rotating extended H I disks are surprisingly self-similar up to high masses, which hints at mass-independent self-regulation mechanisms that have yet to be fully understood.
|
[
1560,
356,
602,
591,
864
] |
[
"spiral galaxies",
"dark matter distribution",
"galaxy kinematics",
"galaxy dynamics",
"irregular galaxies"
] |
2022ApJ...932...51A
|
Testing Horndeski Gravity from EHT Observational Results for Rotating Black Holes
|
The Event Horizon Telescope (EHT) collaboration recently unveiled the first image of the supermassive black hole M87*, which exhibited a ring of angular diameter θ <SUB> d </SUB> = 42 ± 3 μas, a circularity deviation of ΔC ≤ 0.1, and also inferred a black hole mass of M = (6.5 ± 0.7) × 10<SUP>9</SUP> M <SUB>⊙</SUB>. This provides a new window onto tests of theories of gravity in the strong-field regime, including probes of violations of the no-hair theorem. It is widely believed that the Kerr metric describes astrophysical black holes, as encapsulated in the critical but untested no-hair theorem. Modeling Horndeski gravity black holes-with an additional hair parameter h besides the mass M and spin a of the Kerr black hole-as the supermassive black hole M87*, we observe that to be a viable astrophysical black hole candidate, the EHT result constrains the (a, h) parameter space. However, a systematic bias analysis indicates that rotating Horndeski black hole shadows may or may not capture Kerr black hole shadows, depending on the parameter values; the latter is the case over a substantial part of the constrained parameter space, allowing Horndeski gravity and general relativity to be distinguishable in the said space, and opening up the possibility of potential modifications to the Kerr metric.
|
[
98,
159,
565,
661,
670
] |
[
"astrophysical black holes",
"black hole physics",
"galactic center",
"gravitation",
"gravitational lensing"
] |
2023RNAAS...7..137K
|
An Astrometric Mass Estimate for (624) Hektor
|
Jupiter Trojans are remnants of the early solar system. In this research note I present and discuss the mass and the bulk density of the largest Jovian Trojan (624) Hektor, obtained from its gravitational interaction with (437759) 2014 GG47.
|
[
72,
2210,
874,
1469,
1715
] |
[
"asteroids",
"asteroid dynamics",
"jupiter trojans",
"small solar system bodies",
"trojan asteroids"
] |
2021PSJ.....2..185S
|
Collisional Evolution of the Inner Zodiacal Cloud
|
The zodiacal cloud is one of the largest structures in the solar system and strongly governed by meteoroid collisions near the Sun. Collisional erosion occurs throughout the zodiacal cloud, yet it is historically difficult to directly measure and has never been observed for discrete meteoroid streams. After six orbits with Parker Solar Probe (PSP), its dust impact rates are consistent with at least three distinct populations: bound zodiacal dust grains on elliptic orbits (α-meteoroids), unbound β-meteoroids on hyperbolic orbits, and a third population of impactors that may be either direct observations of discrete meteoroid streams or their collisional by-products ("β-streams"). The β-stream from the Geminids meteoroid stream is a favorable candidate for the third impactor population. β-streams of varying intensities are expected to be produced by all meteoroid streams, particularly in the inner solar system, and are a universal phenomenon in all exozodiacal disks. We find the majority of collisional erosion of the zodiacal cloud occurs in the range of 10-20 solar radii and expect this region to also produce the majority of pickup ions due to dust in the inner solar system. A zodiacal erosion rate of at least ~100 kg s<SUP>-1</SUP> and flux of β-meteoroids at 1 au of (0.4-0.8) × 10<SUP>-4</SUP> m<SUP>-2</SUP> s<SUP>-1</SUP> are found to be consistent with the observed impact rates. The β-meteoroids investigated here are not found to be primarily responsible for the inner source of pickup ions, suggesting nanograins susceptible to electromagnetic forces with radii below ~50 nm are the inner source of pickup ions. We expect the peak deposited energy flux to PSP due to dust to increase in subsequent orbits, up to 7 times that experienced during its sixth orbit.
|
[
236,
821,
363,
1040,
1035
] |
[
"circumstellar dust",
"interplanetary dust",
"debris disks",
"meteoroids",
"meteor streams"
] |
2023ApJ...955..102B
|
AstroSat View of the Neutron Star Low-mass X-Ray Binary GX 340+0
|
Understanding the spectral evolution along the "Z"-shaped track in the hardness-intensity diagram of Z sources, which are a class of luminous neutron star low-mass X-ray binaries, is crucial to probe accretion processes close to the neutron star. Here, we study the horizontal branch (HB) and the normal branch (NB) of the Z source GX 340+0 using AstroSat data. We find that the HB and the NB appear as two different types of X-ray intensity dips, which can appear in any sequence and with various depths. Our 0.8-25 keV spectra of dips and the hard apex can be modeled by the emissions from an accretion disk, a Comptonizing corona covering the inner disk, and the neutron star surface. We find that as the source moves onto the HB, the corona is replenished and energized by the disk and a reduced amount of disk matter reaches the neutron star surface. We also conclude that quasiperiodic oscillations during HB/NB are strongly associated with the corona and explain the evolution of strength and hard lag of this timing feature using the estimated coronal optical depth evolution.
|
[
1811,
14,
1579
] |
[
"x-ray binary stars",
"accretion",
"stellar accretion disks"
] |
2022ApJ...929...75P
|
Validation of a Wave Heated 3D MHD Coronal-wind Model using Polarized Brightness and EUV Observations
|
The physical properties responsible for the formation and evolution of the corona and heliosphere are still not completely understood. 3D MHD global modeling is a powerful tool to investigate all the possible candidate processes. To fully understand the role of each of them, we need a validation process where the output from the simulations is quantitatively compared to the observational data. In this work, we present the results from our validation process applied to the wave turbulence driven 3D MHD corona-wind model WindPredict-AW. At this stage of the model development, we focus the work to the coronal regime in quiescent condition. We analyze three simulation results, which differ by the boundary values. We use the 3D distributions of density and temperature, output from the simulations at the time of around the first Parker Solar Probe perihelion (during minimum of the solar activity), to synthesize both extreme ultraviolet (EUV) and white-light-polarized (WL pB) images to reproduce the observed solar corona. For these tests, we selected AIA 193 Å, 211 Å, and 171 Å EUV emissions, MLSO K-Cor, and LASCO C2 pB images obtained on 2018 November 6 and 7. We then make quantitative comparisons of the disk and off limb corona. We show that our model is able to produce synthetic images comparable to those of the observed corona.
|
[
1966,
1476,
1989,
1486,
1483,
1493,
1521,
1477
] |
[
"magnetohydrodynamical simulations",
"solar physics",
"solar coronal heating",
"solar coronal streamers",
"solar corona",
"solar extreme ultraviolet emission",
"solar radiation",
"solar atmosphere"
] |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.