adsabs/SciX_UAT_keywords huggingface dataset:
The First Fall is the Hardest: The Importance of Peculiar Galaxy Dynamics at Infall Time for Tidal Stripping Acting at the Centers of Groups and Clusters

Using dark-matter-only N-body cosmological simulations, we measure the pericentre distance of dark matter halos on their first infall into group and cluster halos. We find that the pericentre distance (R peri) is an important parameter as it significantly affects the strength of tidal mass loss in dense environments, and likely other environmental mechanisms as well. We examine what determines the R peri value and find that, for most infallers, the dominant parameter is V ⊥, the tangential component of the orbital velocity as the halo enters the group/cluster halo for the first time. This means that the strength of tidal stripping acting near the cores of groups/clusters are strongly influenced by the external peculiar velocity field of the large-scale structure surrounding them, which differs between clusters and is sensitive to the mass ratio of infaller to host. We find that filament feeding also partially contributes to feeding in low-V ⊥ halos. Dynamical friction can also play a role in reducing R peri but this is only significant for those few relatively massive infallers (>10% of the mass of their host). These results highlight how the response of galaxies to dense environments will sensitively depend on dynamics inherited from far outside those dense environments.

Keywords: galaxy dark matter halos; n-body simulations; galaxy clusters; galaxy groups; orbits; large-scale structure of the universe
Increasing Activity in T CrB Suggests Nova Eruption Is Impending

Estimates of the accretion rate in symbiotic recurrent novae (RNe) often fall short of theoretical expectations by orders of magnitude. This apparent discrepancy can be resolved if the accumulation of mass by the white dwarf (WD) is highly sporadic, and most observations are performed during low states. Here we use a re-analysis of archival data from the Digital Access to a Sky Century @Harvard survey to argue that the most recent nova eruption in symbiotic RN T CrB, in 1946, occurred during—and was therefore triggered by—a transient accretion high state. Based on similarities in the optical light curve around 1946 and the time of the prior eruption, in 1866, we suggest that the WD in T CrB accumulates most of the fuel needed to ignite the thermonuclear runaways (TNRs) during accretion high states. A natural origin for such states is dwarf-nova like accretion-disk instabilities, which are expected in the presumably large disks in symbiotic binaries. The timing of the TNRs in symbiotic RNe could thus be set by the stability properties of their accretion disks. T CrB is in the midst of an accretion high state like the ones we posit led to the past two nova eruptions. Combined with the approach of the time at which a TNR would be expected based on the 80 yr interval between the prior two novae (2026 ± 3), the current accretion high state increases the likelihood of a TNR occurring in T CrB in the next few years.

Keywords: recurrent novae; symbiotic binary stars; accretion
The Carnegie-Chicago Hubble Program. IX. Calibration of the Tip of the Red Giant Branch Method in the Megamaser Host Galaxy, NGC 4258 (M106)

In the nearby galaxy NGC 4258, the well-modeled orbital motion of H2O masers about its supermassive black hole provides the means to measure a precise geometric distance. As a result, NGC 4258 is one of a few "geometric anchors" available to calibrate the true luminosities of stellar distance indicators such as the Tip of the Red Giant Branch (TRGB) or the Cepheid Leavitt law. In this paper, we present a detailed study of the apparent magnitude of the TRGB within NGC 4258, using publicly available HST observations optimally situated in the unreddened stellar halo along the minor axis, spanning distances ranging from 8 to 22 kpc in projected galactocentric radius, or $6^{\prime} $ (13 kpc) to $30^{\prime} $ (66 kpc) in distance along the semimajor axis. We undertake a systematic evaluation of the uncertainties associated with measuring the TRGB in this galaxy, based on an analysis of 54 arcmin2 of HST/ACS imaging. After quantifying these uncertainties, we measure the TRGB in NGC 4258 to be F814W0 = 25.347 ± 0.014 (stat) ± 0.042 (sys) mag. Combined with a recent 1.5% megamaser distance to NGC 4258, we determine the absolute luminosity of the TRGB to be ${M}_{{\rm{F}}814{\rm{W}}}^{{\rm{TRGB}}}=-4.050\pm 0.028$ (stat) ± 0.048 (sys) mag. This new calibration agrees to better than 1% with an independent calibration presented in Freedman et al. that was based on detached eclipsing binaries (DEBs) located in the LMC. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO-9477 and GO-10399.

Keywords: distance measure; galaxy distances; stellar distance; linear regression; stellar populations; population ii stars; galaxy stellar halos; galaxy stellar disks
Dramatic Drop in the X-Ray Polarization of Swift J1727.8–1613 in the Soft Spectral State

Black hole X-ray binaries exhibit different spectral and timing properties in different accretion states. The X-ray outburst of a recently discovered and extraordinarily bright source, Swift J1727.8–1613, has enabled the first investigation of how the X-ray polarization properties of a source evolve with spectral state. The 2–8 keV polarization degree was previously measured by the Imaging X-ray Polarimetry Explorer (IXPE) to be ≈4% in the hard and hard intermediate states. Here we present new IXPE results taken in the soft state, with the X-ray flux dominated by the thermal accretion disk emission. We find that the polarization degree has dropped dramatically to ≲1%. This result indicates that the measured X-ray polarization is largely sensitive to the accretion state and the polarization fraction is significantly higher in the hard state when the X-ray emission is dominated by upscattered radiation in the X-ray corona. The combined polarization measurements in the soft and hard states disfavor a very high or low inclination of the system.

Keywords: black hole physics; x-ray astronomy; polarimetry; stellar mass black holes
GRIT: A Package for Structure-Preserving Simulations of Gravitationally Interacting Rigid Bodies

The spin-orbit coupling of planetary systems plays an important role in the dynamics and habitability of planets. However, symplectic integrators that can accurately simulate not only how orbit affects spin but also how spin affects orbit have not been constructed for general systems. Thus, we develop symplectic Lie-group integrators to simulate systems consisting gravitationally interacting rigid bodies. A user friendly package (GRIT3 ) is provided and external forcings, such as tidal interactions, are also included. As a demonstration, this package is applied to Trappist-I. The results show that the differences in transit-timing variations due to spin-orbit coupling could reach a few min in 10-year measurements, and strong planetary perturbations can push Trappist-I f, g and h out of the synchronized states.

Keywords: exoplanet dynamics; planetary dynamics; celestial mechanics; few-body systems; black hole spin-flip; oblateness
Multiple Stellar Populations at Less-evolved Stages-II: No Evidence of Significant Helium Spread among NGC 1846 Dwarfs

The detection of star-to-star chemical variations in star clusters older than 2 Gyr has changed the traditional view of star clusters as canonical examples of "simple stellar populations" into the so-called "multiple stellar populations" (MPs). Although the significance of MPs seems to correlate with cluster total mass, it seems that the presence of MPs is determined by cluster age. In this article, we use deep photometry from the Hubble Space Telescope to investigate whether the FG-type dwarfs in the ~1.7 Gyr old cluster NGC 1846, have helium spread. By comparing the observation with the synthetic stellar populations, we estimate a helium spread of ΔY ~ 0.01 ± 0.01 among the main-sequence stars in NGC 1846. The maximum helium spread would not exceed ΔY ~ 0.02, depending on the adopted fraction of helium-enriched stars. To mask the color variation caused by such a helium enrichment, a nitrogen enrichment of at least Δ[N/Fe] = 0.8 dex is required, which is excluded by previous analyses of the red-giant branch in this cluster. We find that our result is consistent with the ΔY-mass relationship for Galactic globular clusters. To examine whether or not NGC 1846 harbors MPs, higher photometric accuracy is required. We conclude that under the adopted photometric quality, there is no extreme helium variation among NGC 1846 dwarfs.

Keywords: star clusters; hertzsprung russell diagram; large magellanic cloud; stellar populations
On the Structure of the Sagittarius Spiral Arm in the Inner Milky Way

We report measurements of trigonometric parallax and proper motion for two 6.7 GHz methanol and two 22 GHz water masers located in the far portion of the Sagittarius spiral arm as part of the BeSSeL Survey. Distances for these sources are estimated from parallax measurements combined with three-dimensional kinematic distances. The distances of G033.64‑00.22, G035.57‑00.03, G041.15‑00.20, and G043.89‑00.78 are 9.9 ± 0.5, 10.2 ± 0.6, 7.6 ± 0.5, and 7.5 ± 0.3 kpc, respectively. Based on these measurements, we suggest that the Sagittarius arm segment beyond about 8 kpc from the Sun in the first Galactic quadrant should be adjusted radially outward relative to previous models. This supports the suggestion of Xu et al. that the Sagittarius and Perseus spiral arms might merge in the first quadrant before spiraling inward to the far end of the Galactic bar.

Keywords: interstellar masers; trigonometric parallax; star forming regions; milky way galaxy
Atmospheric Dust Causes Darkness to Fall Rapidly on Mars

On mission sol 783 (at Martian solar longitude (LS) of 217°), Mars Science Laboratory's MastCam instrument imaged a faint glow, extending upwards from the horizon (Figure 1(a)). The images were acquired from 18:58 to 19:01 LTST, nearly an hour after sunset occurred at 18:05 LTST, providing an opportunity to examine illumination in the Martian sky around sunset. The radiance of the observed glow is small when compared to daytime sky brightness values, with an average value between 20 and 35 μW m-2 Sr-1, and appears brightest in the blue filter (the average B/R ratio is 1.25). The total flux at the time of the measurement was calculated to be 4.2 × 10-4 W m-2, nearly three orders of magnitude dimmer than what would be expected for an Earth-like Atmosphere. An observer on the surface of Mars would thus find twilight becoming deeper much more rapidly than on the Earth.

Keywords: mars; planetary atmospheres; optical observation; twilight
Linking Soft Excess in Ultraluminous X-Ray Sources with Optically Thick Wind Driven by Supercritical Accretion

Supercritical accretion onto compact objects may drive massive winds that are nearly spherical, optically thick, and Eddington limited. Blackbody emission from the photosphere is the direct observational signature of the wind. Here we investigate whether or not it can explain the soft emission component seen in the energy spectra of ultraluminous X-ray sources (ULXs). Based on high-quality XMM-Newton spectra of 15 ULXs, we find that the soft component can be modeled as blackbody emission with a nearly constant luminosity, and the five known pulsating ULXs (PULXs) in the sample display a blackbody luminosity among the lowest. These are consistent with the scenario that the soft emission originates from the photosphere of the optically thick wind. However, the derived blackbody luminosity for PULXs is significantly above the Eddington limit for neutron stars. A possible explanation is that a considerable fraction of the optically thick wind roots in the inner accretion flow, where the radiative flux could exceed the Eddington limit due to a reduced scattering cross-section or enhanced radiation transfer with magnetic buoyancy. Based on a wind model, the inferred mass accretion rate in these standard ULXs overlaps but is on average lower than that in luminous and very soft X-ray sources, which are also candidates with supercritical accretion. Alternatively, it cannot be ruled out that the soft emission component is a result of the hard component, e.g., via down-scattering in a cool medium, as a weak correlation may exist between them.

Keywords: compact objects; x-ray binary stars; stellar accretion; x-ray sources
Eruption of the Envelope of Massive Stars by Energy Injection with Finite Duration

A significant fraction of supernovae show signatures of dense circumstellar material (CSM). While multiple scenarios for creating a dense CSM exist, mass eruption due to injection of energy at the base of the outer envelope is a likely possibility. We carry out radiation hydrodynamical simulations of eruptive mass loss from a typical red supergiant progenitor with an initial mass of 15 M ⊙, for the first time focusing on the timescale of the injection as well as energy. We find that not only sufficient injection energy but also sufficient rate of energy injection per unit time, L min ~ 8 × 1040 erg s-1 in this particular model, is required for eruption of unbound CSM. This result suggests that the energy injection rate needs to be greater than the binding energy of the envelope divided by the dynamical timescale for the eruption. The density profile of the resulting CSM, whose shape was analytically and numerically predicted in the limit of instantaneous energy injection, similarly holds for a finite injection timescale. We discuss our findings in the framework of proposed mass outburst scenarios, specifically wave-driven outbursts and common-envelope ejection.

Keywords: stellar mass loss
The Physical Parameters of Clumps Associated with Class I Methanol Masers

We present a study of the association between class I methanol masers and cold dust clumps from the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) survey. It was found that almost 100% of class I methanol masers are associated with objects listed in the ATLASGAL compact source catalog. We find a statistically significant difference in the flux density, luminosity, number and column density, and temperature distributions of ATLASGAL sources associated with 95/44 GHz methanol masers compared with those ATLASGAL sources devoid of 95 GHz methanol masers. The masers tend to arise in clumps with higher densities, luminosities, and temperatures compared with both the full sample of ATLASGAL clumps, as well as the sample of ATLASGAL sources that were cross-matched with positions previously searched for methanol masers but with no detections. Comparison between the peak position of ATLASGAL clumps and the interferometric positions of the associated class I and II methanol masers reveals that class I masers are generally located at larger physical distances from the peak submillimeter emission than class II masers. We conclude that the tight association between ATLASGAL sources and class I methanol masers may be used as a link toward understanding the conditions of the pumping of these masers and evolutionary stages at which they appear.

Keywords: astrophysical masers; interstellar medium; astronomy databases; dust continuum emission
New Surface Abundances for HD 216494 (74 Aqr)

New abundances are derived for the brightest member of 74 Aqr. The profile of the Mg II line at 4481 Å is composite and clearly shows three components which confirms the classification of 74 Aqr as a triple SB3 system. The derived abundance pattern confirms the HgMn nature of this star. Helium and magnesium are found to be more deficient than in previous studies while phosphorus is less overabundant.

Keywords: chemically peculiar stars
The Birth Function for Black Holes and Neutron Stars in Close Binaries

The mass function for black holes and neutron stars at birth is explored for mass-losing helium stars. These should resemble, more closely than similar studies of single hydrogen-rich stars, the results of evolution in close binary systems. The effects of varying the mass-loss rate and metallicity are calculated using a simple semi-analytic approach to stellar evolution that is tuned to reproduce detailed numerical calculations. Though the total fraction of black holes made in stellar collapse events varies considerably with metallicity, mass-loss rate, and mass cutoff, from 5% to 30%, the shapes of their birth functions are very similar for all reasonable variations in these quantities. Median neutron star masses are in the range 1.32-1.37 ${M}_{\odot }$ regardless of metallicity. The median black hole mass for solar metallicity is typically 8-9 ${M}_{\odot }$ if only initial helium cores below 40 ${M}_{\odot }$ (ZAMS mass less than 80 ${M}_{\odot }$ ) are counted, and 9-13 ${M}_{\odot }$, in most cases, if helium cores with initial masses up to 150 ${M}_{\odot }$ (ZAMS mass less than 300 ${M}_{\odot }$ ) contribute. As long as the mass-loss rate as a function of mass exhibits no strong nonlinearities, the black hole birth function from 15 to 35 ${M}_{\odot }$ has a slope that depends mostly on the initial mass function for main-sequence stars. These findings imply the possibility of constraining the initial mass function and the properties of mass loss in close binaries using ongoing measurements of gravitational-wave radiation. The expected rotation rates of the black holes are briefly discussed.

Keywords: stellar mass black holes; core-collapse supernovae; neutron stars; stellar mass loss; close binary stars; stellar evolutionary models; massive stars
Modeling Nitrogen Fractionation in the Protoplanetary Disk around TW Hya: Model Constraints on Grain Population and Carbon-to-oxygen Elemental Abundance Ratio

Observations conducted using the Atacama Large Millimeter/submillimeter Array on the protoplanetary disk around TW Hya show the nitrogen fractionation of HCN molecules in HC14N/HC15N ∼ 120 at a radius of ∼20 au. In this study, we investigate the physical and chemical conditions that control this nitrogen fractionation process. To this end, a new disk model was developed, in which the isotope-selective photodissociation of N2 and isotope-exchange chemical reactions have been incorporated. Our model can successfully reproduce the observed HCN column density when the elemental abundances of gas-phase carbon and oxygen are depleted by two orders of magnitude relative to those in the interstellar medium and carbon is more abundant than oxygen ([C/O]elem > 1). The isotope-selective photodissociation of N2 is the dominant nitrogen fractionation process in our models. The observed HC14N/HC15N ratio, which increases outwards, can also be reproduced by the model by assuming that the small dust grains in the atmosphere of the outer disk are depleted more than those in the inner disk. This is consistent with grain evolution models, according to which small dust grains are continuously replenished in the inner disk due to fragmentation of the large dust grains that radially drift from the outer disk.

Keywords: protoplanetary disks; astrochemistry
SN 2020uem: a Possible Thermonuclear Explosion within a Dense Circumstellar Medium (II). The Properties of the CSM from Polarimetry and Light-curve Modeling

Type IIn/Ia-CSM supernovae (SNe IIn/Ia-CSM) are classified by their characteristic spectra, which exhibit narrow hydrogen emission lines originating from strong interaction with a circumstellar medium (CSM) together with broad lines of intermediate-mass elements. We performed intensive follow-up observations of SN IIn/Ia-CSM 2020uem, including photometry, spectroscopy, and polarimetry. In this paper, we focus on the results of polarimetry. We performed imaging polarimetry at 66 days and spectropolarimetry at 103 days after discovery. SN 2020uem shows a high continuum polarization of 1.0%-1.5% without wavelength dependence. Besides, the polarization degree and position angle keep roughly constant. These results suggest that SN 2020uem is powered by strong interaction with a confined and aspherical CSM. We performed simple polarization modeling, based on which we suggest that SN 2020uem has an equatorial-disk/torus CSM. Besides, we performed semi-analytic light-curve modeling and estimated the CSM mass. We revealed that the mass-loss rate in the final few hundred years immediately before the explosion of SN 2020uem is in the range of 0.01-0.05 M ⊙ yr-1, and that the total CSM mass is 0.5-4 M ⊙. The CSM mass can be accommodated by not only a red supergiant (RSG), but also by a red giant (RG) or an asymptotic giant branch (AGB) star. As a possible progenitor scenario of SN 2020uem, we propose a white dwarf binary system including an RG, RSG, or AGB star, especially a merger scenario via common envelope evolution, i.e., the core-degenerate scenario or a variant.

Keywords: supernovae; supernova dynamics; circumstellar matter; polarimetry; spectropolarimetry
What Determines Active Region Coronal Plasma Composition?

The chemical composition of the solar corona is different from that of the solar photosphere, with the strongest variation being observed in active regions (ARs). Using data from the Extreme Ultraviolet (EUV) Imaging Spectrometer (EIS) on Hinode, we present a survey of coronal elemental composition as expressed in the first ionization potential (FIP) bias in 28 ARs of different ages and magnetic flux content, which are at different stages in their evolution. We find no correlation between the FIP bias of an AR and its total unsigned magnetic flux or age. However, there is a weak dependence of FIP bias on the evolutionary stage, decreasing from 1.9 to 2.2 in ARs with spots to 1.5-1.6 in ARs that are at more advanced stages of the decay phase. FIP bias shows an increasing trend with average magnetic flux density up to 200 G, but this trend does not continue at higher values. The FIP bias distribution within ARs has a spread between 0.4 and 1. The largest spread is observed in very dispersed ARs. We attribute this to a range of physical processes taking place in these ARs, including processes associated with filament channel formation. These findings indicate that, while some general trends can be observed, the processes influencing the composition of an AR are complex and specific to its evolution, magnetic configuration, or environment. The spread of FIP bias values in ARs shows a broad match with that previously observed in situ in the slow solar wind.

Keywords: solar active regions; solar abundances