adsabs/SciX_UAT_keywords huggingface dataset:
Informing the Cataclysmic Variable Sequence from Gaia Data: The Orbital-period-Color-Absolute-magnitude Relationship

The orbital-period (P orb) gap in the population of cataclysmic variables (CVs) informs the theoretical narrative of CV evolution, yet a complete understanding of the driving angular momentum loss mechanisms above and below this gap remains elusive. Here we identify, for standard CVs, a new, apparently monotonic relationship between quiescent color (G BP-G RP), absolute magnitude (M G ), and P orb (between 70 minutes and 8 hr) revealed in Gaia DR2 and EDR3. We show that P orb increases in the color-absolute-magnitude diagram roughly orthogonally to the white dwarf and main sequences. We find the orbital-period-color-absolute-magnitude relationship to be stable across different CV subtypes: dwarf novae, intermediate polars, polars, and novalike systems. We place our findings in context with the known semiempirical donor sequence for CVs and find a dependence between color and M G for a given P orb specifically for dwarf novae and intermediate polars above the period gap. These relations have the potential to inform a more complete picture of CV evolution.

Keywords: cataclysmic variable stars; variable stars; surveys; hertzsprung russell diagram; close binary stars
Observational Constraints on the Metagalactic Lyα Photon Scattering Rate at High Redshift

The scattering of Lyα photons from the first radiating sources in the universe plays a pivotal role in 21 cm radio detections of Cosmic Dawn and the Epoch of Reionization through the Wouthuysen-Field effect. New data from JWST show the Lyα photon scattering rate exceeds that required to decouple the intergalactic hydrogen spin temperature from that of the Cosmic Microwave Background up to z ~ 14 and render the neutral hydrogen visible.

Keywords: cosmology; reionization; intergalactic medium
Crystallization Kinetics of Vitreous Magnesium Sulfate Hydrate and Implications for Europa's Surface

Brines consistent with that expected for Europa's global subsurface ocean have been shown to form vitreous salt hydrates when frozen. We report experiments examining the crystallization kinetics of vitreous MgSO4 hydrate in order to better understand the stability of such materials on the surface of Europa. Vitreous MgSO4 hydrates formed from a 2 M parent solution were found to crystallize into MgSO4·11H2O (meridianiite) upon annealing at 195-225 K. Raman spectroscopy was used to monitor the crystallization and reaction rates were determined from the growth of the crystalline fraction as a function of time. Arrhenius analysis yielded an activation energy of 60 ± 9 kJ mol-1 for the vitreous to crystalline transition, implying that such transformation does not occur spontaneously at Europa's surface temperatures. If emplacement processes favor the formation of vitreous salt hydrates, they are likely to still be stable and could be an important non-ice component on Europa at present day.

Keywords: europa; surface ices; chemical kinetics; ice spectroscopy
Disentangling the Signatures of Blended-light Atmospheres in L/T Transition Brown Dwarfs

We present a technique to identify spectrophotometrically variable L7-T3 brown dwarfs with single-epoch, low-resolution, near-infrared SpeX spectra. We calculated spectral indices on known variable brown dwarfs and used them to select 11 index-index parameter spaces where known variables can be distinguished from the rest of the general population of brown dwarfs. We find 62 candidate variables, 12 of which show significant variability amplitude in independent photometric monitoring surveys. This technique constitutes the first formal method to identify a time-dependent effect such as variability from peculiarities in their integrated light spectra. This technique will be a useful tool to prioritize targets for future photometric and spectroscopic monitoring in the era of the James Webb Space Telescope and 30 m-class telescopes.

Keywords: brown dwarfs; l dwarfs; t dwarfs; atmospheric variability; astronomical techniques; spectroscopy; near infrared astronomy
Detecting New Visual Binaries in Gaia DR3 with Gaia and Two Micron All Sky Survey (2MASS) Photometry. I. New Candidate Binaries within 200 pc of the Sun

We present a method to identify likely visual binaries in Gaia eDR3 that does not rely on parallax or proper motion. This method utilizes the various point-spread function sizes of Two Micron All Sky Survey (2MASS)/Gaia, where at <2.″5 two stars may be unresolved in 2MASS but resolved by Gaia. Due to this, if close neighbors listed in Gaia are a resolved pair, the associated 2MASS source will have a predictable excess in the J band that depends on the ΔG of the pair. We demonstrate that the expected relationship between 2MASS excess and ΔG differs for chance alignments, as compared to true binary systems, when parameters like magnitude and location on the sky are also considered. Using these multidimensional distributions, we compute the likelihood of a close pair of stars to be a chance alignment, resulting in a total(clean) catalog of 68,725(50,230) likely binaries within 200 pc with a completeness rate of ~75%(~64%) and contamination rate of ~14%(~0.4%). Within this, we find 590 previously unidentified binaries from Gaia eDR3 with projected physical separations <30 au, where 138 systems were previously identified, and for s < 10 au we find that 4 out of 15 new likely binaries have not yet been observed with high-resolution imaging. We also demonstrate the potential of our catalog to determine physical separation distributions and binary fraction estimates, from this increase in low-separation binaries. Overall, this catalog provides a good complement for the study of local binary populations by probing smaller physical separations and mass ratios, and provides prime targets for speckle monitoring.

Keywords: close binary stars; catalogs; visual binary stars
Long-rising Type II Supernovae in the Zwicky Transient Facility Census of the Local Universe

SN 1987A was an unusual hydrogen-rich core-collapse supernova originating from a blue supergiant star. Similar blue supergiant explosions remain a small family of events, and are broadly characterized by their long rises to peak. The Zwicky Transient Facility Census of the Local Universe (CLU) experiment aims to construct a spectroscopically complete sample of transients occurring in galaxies from the CLU galaxy catalog. We identify 13 long-rising (>40 days) Type II supernovae from the volume-limited CLU experiment during a 3.5 yr period from 2018 June to 2021 December, approximately doubling the previously known number of these events. We present photometric and spectroscopic data of these 13 events, finding peak r-band absolute magnitudes ranging from -15.6 to -17.5 mag and the tentative detection of Ba II lines in nine events. Using our CLU sample of events, we derive a long-rising Type II supernova rate of ${1.37}_{-0.30}^{+0.26}\times {10}^{-6}$ Mpc-3 yr-1, ≈1.4% of the total core-collapse supernova rate. This is the first volumetric rate of these events estimated from a large, systematic, volume-limited experiment.

Keywords: core-collapse supernovae; supernovae; type ii supernovae; galaxies; sky surveys; surveys; spectroscopy
Elimination of the Blue Loops in the Evolution of Intermediate-mass Stars by the Neutrino Magnetic Moment and Large Extra Dimensions

For searching beyond Standard Model physics, stars are laboratories that complement terrestrial experiments. Massless neutrinos in the Standard Model of particle physics cannot have a magnetic moment, but massive neutrinos have a finite magnetic moment in the minimal extension of the Standard Model. Large extra dimensions (LEDs) are a possible solution of the hierarchy problem. Both of these provide additional energy-loss channels in stellar interiors via the electromagnetic interaction and radiation into extra dimensions, respectively, and thus affect stellar evolution. We perform simulations of stellar evolution with such additional energy losses and find that they eliminate the blue loops in the evolution of intermediate-mass stars. The existence of Cepheid stars can be used to constrain the neutrino magnetic moment (NMM) and LEDs. In order for Cepheids to exist, the NMM should be smaller than the range ∼2 × 10-10μB-4 × 10-11μB, where μB is the Bohr magneton, and the fundamental scale in the (4+2)-spacetime should be larger than ∼2-5 TeV, depending on the rate of the 12C ${(\alpha ,\gamma )}^{16}{\rm{O}}$ reaction. The fundamental scale also has strong dependence on the metallicity. This value of the magnetic moment is in the range explored in the reactor experiments, but higher than the limit inferred from globular clusters. Similarly the fundamental scale value we constrain corresponds to a size of the compactified dimensions comparable to those explored in the torsion balance experiments, but it is smaller than the limits inferred from collider experiments and low-mass stars.

Keywords: non-standard theories of gravity; stellar evolution; cepheid variable stars; neutrino astronomy; particle astrophysics
Self-gravitating Equilibria of Non-minimally Coupled Dark Matter Halos

We investigate self-gravitating equilibria of halos constituted by dark matter (DM) non-minimally coupled to gravity. In particular, we consider a theoretically motivated non-minimal coupling that may arise when the averaging/coherence length L associated with the fluid description of the DM collective behavior is comparable to the local curvature scale. In the Newtonian limit, such a non-minimal coupling amounts to a modification of the Poisson equation by a term L2∇2ρ proportional to the Laplacian of the DM density ρ itself. We further adopt a general power-law equation of state p ∝ ρΓrα relating the DM dynamical pressure p to density ρ and radius r, as expected for phase-space density stratification during the gravitational assembly of halos in a cosmological context. We confirm previous findings that, in the absence of non-minimal coupling, the resulting density ρ(r) features a steep central cusp and an overall shape mirroring the outcomes of N-body simulations in the standard ΛCDM cosmology, as described by the classic Navarro-Frenk-White or Einasto profiles. Most importantly, we find that the non-minimal coupling causes the density distribution to develop an inner core and a shape that closely follows the Burkert profile out to several core scale radii. In fact, we highlight that the resulting mass distributions can fit, with an accuracy comparable to Burkert's one, the coadded rotation curves of dwarf, DM-dominated galaxies. Finally, we show that non-minimally coupled DM halos are consistent with the observed scaling relation between the core radius r0 and core density ρ0, in terms of a universal core surface density ρ0 × r0 among different galaxies.

Keywords: cosmology; dark matter; non-standard theories of gravity
Comparison of Enhanced Absorption in He I 10830 Šin Observations and Modeling during the Early Phase of a Solar Flare

The He I 10830 Å triplet is a very informative indicator of chromospheric activities as the helium is the second most abundant element in the solar atmosphere. Taking advantage of the high resolution of the 1.6 m Goode Solar Telescope at Big Bear Solar Observatory, previous observations have shown clear evidence of the enhanced absorption, instead of typically observed emission, for two M-class flares. In this study, we analyze the evolution of the He I 10830 Å emission in numerical models and compare it with observations. The models represent the RADYN simulation results obtained from the F-CHROMA database. We consider the models with the injected electron spectra parameters close to observational estimates for the 2013 August 17 flare event (δ = 8, ${E}_{c}=\{15,20\}\,\,\mathrm{keV}$ , $F=\{1\times {10}^{11},3\times {10}^{11}\}\,\mathrm{erg}\,{\mathrm{cm}}^{-2}$ ) in detail, as well as other available models. The modeling results agree well with observations, in the sense of both the maximum intensity decrease (-17.1%, compared with the observed value of -13.7%) and the trend of temporal variation (initial absorption phase followed by the emission). All models demonstrate the increased number densities and decreased ratio of the upper and lower level populations of the He I 10830 Å transition in the initial phase, which enhances the opacity and forms an absorption feature. Models suggest that the temperatures and free electron densities at heights of 1.3-1.5 Mm should be larger than ∼104 K and 6 × 1011 cm-3 thresholds for the line to start being in emission.

Keywords: solar activity; solar chromosphere; solar flares
Outflows in the Presence of Cosmic Rays and Waves

Plasma outflow or wind against a gravitational potential under the influence of cosmic rays is studied in the context of hydrodynamics. Cosmic rays interact with the plasma via hydromagnetic fluctuations. In the process, cosmic rays advect and diffuse through the plasma. We adopt a multi-fluid model in which, besides thermal plasma, cosmic rays and self-excited Alfvén waves are also treated as fluids. We seek possible, physically allowable steady-state solutions of three-fluid (one Alfvén wave) and four-fluid (two Alfvén waves) models with given boundary conditions at the base of the potential well. Generally speaking, there are two classes of outflows—subsonic and supersonic (with respect to a suitably defined sound speed). A three-fluid model without cosmic-ray diffusion can be studied in the same way as the classic stellar wind problem, and is taken as a reference model. When cosmic-ray diffusion is included, there are two categories of solutions. One of them resembles the three-fluid model without diffusion, and the other behaves like thermal wind at large distances when the waves wither and cosmic rays are decoupled from the plasma. We also examine the effect of wave damping mechanisms (such as nonlinear Landau damping). Roughly speaking, the effect is much smaller in supersonic outflow than in subsonic outflow.

Keywords: cosmic rays; galactic winds; hydrodynamics; alfven waves; stellar winds
A Large-scale Magneto-ionic Fluctuation in the Local Environment of Periodic Fast Radio Burst Source FRB 20180916B

Fast radio burst (FRB) source FRB 20180916B exhibits a 16.33-day periodicity in its burst activity. It is as of yet unclear what proposed mechanism produces the activity, but polarization information is a key diagnostic. Here we report on the polarization properties of 44 bursts from FRB 20180916B detected between 2018 December and 2021 December by CHIME/FRB, the FRB project on the Canadian Hydrogen Intensity Mapping Experiment. In contrast to previous observations, we find significant variations in the Faraday rotation measure (RM) of FRB 20180916B. Over the 9-month period 2021 April and 2021 December we observe an apparent secular increase in RM of ~50 rad m-2 (a fractional change of over 40%) that is accompanied by a possible drift of the emitting band to lower frequencies. This interval displays very little variation in the dispersion measure (ΔDM ≲ 0.8 pc cm-3), which indicates that the observed RM evolution is likely produced from coherent changes in the Faraday-active medium's magnetic field. Burst-to-burst RM variations appear unrelated to the activity cycle phase. The degree of linear polarization of our burst sample (≳80%) is consistent with the negligible depolarization expected for this source in the 400-800 MHz bandpass of CHIME. FRB 20180916B joins other repeating FRBs in displaying substantial RM evolution. This is consistent with the notion that repeater progenitors may be associated with young stellar populations by their preferential occupation of dynamic magnetized environments commonly found in supernova remnants, in pulsar wind nebulae, or near high-mass stellar companions.

Keywords: radio transient sources; magnetic fields; spectropolarimetry; interstellar medium
Stellar Mass and Stellar Mass-to-light Ratio-Color Relations for Low Surface Brightness Galaxies

We estimate the stellar mass for a sample of low surface brightness galaxies (LSBGs) by fitting their multiband spectral energy distributions (SEDs) to the stellar population synthesis model. The derived stellar masses (log M*/M⊙) span from 7.1 to 11.1, with a mean of log M*/M⊙ = 8.5, which is lower than that for normal galaxies. The stellar mass-to-light ratio (γ*) in each band varies little with the absolute magnitude but increases with higher M*. This trend of γ* with M* is even stronger in bluer bands. In addition, the γ* for our LSBGs slightly declines from the r band to the longer-wavelength bands. The log ${\gamma }_{* }^{j} (j = g, r, i, and z) have relatively tight relations with optical colors of g - r and g - i. Compared with several representative γ*-color relations (MLCRs) from the literature, our MLCRs based on LSBG data are consistently among those literature MLCRs previously defined on diverse galaxy samples, and the existing minor differences between the MLCRs are caused by the differences in the SED model ingredients (including initial mass function, star formation history, and stellar population model), line fitting techniques, galaxy samples, and photometric zero-point, rather than the galaxy surface brightness itself, which distinguishes LSBGs from high surface brightness galaxies. Our LSBGs would be very likely to follow those representative MLCRs previously defined in diverse galaxy populations, if those main ingredients were taken into account.

Keywords: low surface brightness galaxies; mass-to-light ratio; surface photometry; galaxy masses
Depolarization of MgH Solar Lines by Collisions with Hydrogen Atoms

Interpretations of the very rich second solar spectrum of the MgH molecule face serious problems owing to the complete lack of any information about rates of collisions between the MgH and hydrogen atoms. This work seeks to begin the process of filling this lacuna by providing, for the first time, quantum excitation, depolarization, and polarization transfer collisional rates of the MgH ground state X2Σ. To achieve the goals of this work, potential energy surfaces are calculated and then are included in the Schrödinger equation to obtain the probabilities of collisions and, thus, all collisional rates. Our rates are obtained for temperatures ranging from T = 2000 to 15,000 K. Sophisticated genetic programming methods are adopted in order to fit all depolarization rates with useful analytical functions of two variables: the total molecular angular momentum and temperatures. We study the solar implications of our results, and we find that the X2Σ state of MgH is partially depolarized by isotropic collisions with neutral hydrogen in its ground state 2S. Our findings show the limits of applicability of the widely used approximation in which the lower-level polarization is neglected.

Keywords: solar physics; solar atmosphere; solar magnetic fields
On the Metallicities and Kinematics of the Circumgalactic Media of Damped Lyα Systems at z 2.5

We use medium- and high-resolution spectroscopy of close pairs of quasars to analyze the circumgalactic medium (CGM) surrounding 32 damped Lyα absorption systems (DLAs). The primary quasar sightline in each pair probes an intervening DLA in the redshift range 1.6 < z abs < 3.5, such that the secondary sightline probes absorption from Lyα and a large suite of metal-line transitions (including O I, C II, C IV, Si II, and Si IV) in the DLA host galaxy's CGM at transverse distances 24 kpc ≤ R ⊥ ≤ 284 kpc. Analysis of Lyα in the CGM sightlines shows an anticorrelation between R ⊥ and H I column density (N HI) with 99.8% confidence, similar to that observed around luminous galaxies. The incidences of C II and Si II with N > 1013 cm-2 within 100 kpc of DLAs are larger by 2σ than those measured in the CGM of Lyman break galaxies (C f (N CII ) > 0.89 and ${{\rm{C}}}_{f}({N}_{\mathrm{Si}{\rm\small{II}}})={0.75}_{-0.17}^{+0.12}$ ). Metallicity constraints derived from ionic ratios for nine CGM systems with negligible ionization corrections and N HI > 1018.5 cm-2 show a significant degree of scatter (with metallicities/limits across the range $-2.06\lesssim \mathrm{log}Z/{Z}_{\odot }\lesssim -0.75$ ), suggesting inhomogeneity in the metal distribution in these environments. Velocity widths of C IV λ1548 and low-ionization metal species in the DLA versus CGM sightlines are strongly (>2σ) correlated, suggesting that they trace the potential well of the host halo over R ⊥ ≲ 300 kpc scales. At the same time, velocity centroids for C IV λ1548 differ in DLA versus CGM sightlines by >100 km s-1 for ~50% of velocity components, but few components have velocities that would exceed the escape velocity assuming dark matter host halos of ≥1012 M ⊙. * 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.

Keywords: circumgalactic medium; damped lyman-alpha systems; quasar absorption line spectroscopy
HAZMAT VI: The Evolution of Extreme Ultraviolet Radiation Emitted from Early M Stars

Quantifying the evolution of stellar extreme ultraviolet (EUV, 100-1000 Å) emission is critical for assessing the evolution of planetary atmospheres and the habitability of M dwarf systems. Previous studies from the HAbitable Zones and M dwarf Activity across Time (HAZMAT) program showed the far- and near-UV (FUV, NUV) emission from M stars at various stages of a stellar lifetime through photometric measurements from the Galaxy Evolution Explorer (GALEX). The results revealed increased levels of short-wavelength emission that remain elevated for hundreds of millions of years. The trend for EUV flux as a function of age could not be determined empirically because absorption by the interstellar medium prevents access to the EUV wavelengths for the vast majority of stars. In this paper, we model the evolution of EUV flux from early M stars to address this observational gap. We present synthetic spectra spanning EUV to infrared wavelengths of 0.4 ± 0.05 M⊙ stars at five distinct ages between 10 and 5000 Myr, computed with the PHOENIX atmosphere code and guided by the GALEX photometry. We model a range of EUV fluxes spanning two orders of magnitude, consistent with the observed spread in X-ray, FUV, and NUV flux at each epoch. Our results show that the stellar EUV emission from young M stars is 100 times stronger than field age M stars, and decreases as t-1 after remaining constant for a few hundred million years. This decline stems from changes in the chromospheric temperature structure, which steadily shifts outward with time. Our models reconstruct the full spectrally and temporally resolved history of an M star's UV radiation, including the unobservable EUV radiation, which drives planetary atmospheric escape, directly impacting a planet's potential for habitability.

Keywords: stellar activity; stellar chromospheres; low mass stars; m stars; ultraviolet astronomy; stellar evolution