adsabs/SciX_UAT_keywords huggingface dataset:
Orbital Decay in an Accreting and Eclipsing 13.7 Minute Orbital Period Binary with a Luminous Donor

We report the discovery of ZTF J0127+5258, a compact mass-transferring binary with an orbital period of 13.7 minutes. The system contains a white dwarf accretor, which likely originated as a post-common envelope carbon-oxygen (CO) white dwarf, and a warm donor (T eff,donor = 16,400 ± 1000 K). The donor probably formed during a common envelope phase between the CO white dwarf and an evolving giant that left behind a helium star or white dwarf in a close orbit with the CO white dwarf. We measure gravitational wave-driven orbital inspiral with ~51σ significance, which yields a joint constraint on the component masses and mass transfer rate. While the accretion disk in the system is dominated by ionized helium emission, the donor exhibits a mixture of hydrogen and helium absorption lines. Phase-resolved spectroscopy yields a donor radial velocity semiamplitude of 771 ± 27 km s-1, and high-speed photometry reveals that the system is eclipsing. We detect a Chandra X-ray counterpart with L X ~ 3 × 1031 erg s-1. Depending on the mass transfer rate, the system will likely either evolve into a stably mass-transferring helium cataclysmic variable, merge to become an R CrB star, or explode as a Type Ia supernova in the next million years. We predict that the Laser Space Interferometer Antenna (LISA) will detect the source with a signal-to-noise ratio of 24 ± 6 after 4 yr of observations. The system is the first LISA-loud mass-transferring binary with an intrinsically luminous donor, a class of sources that provide the opportunity to leverage the synergy between optical and infrared time domain surveys, X-ray facilities, and gravitational-wave observatories to probe general relativity, accretion physics, and binary evolution.

Keywords: close binary stars; eclipsing binary stars; gravitational wave sources; x-ray binary stars
The Differential Assembly History of the Centers and Outskirts of Main-sequence Galaxies at z 2.3

We present a study of spatially resolved star formation histories (SFHs) for 60 z ~ 2.3 main-sequence, star-forming galaxies selected from the MOSDEF spectroscopic survey in the GOODS-N field, with median stellar mass $\mathrm{log}({M}_{\star }/{M}_{\odot })$ = 9.75 and spanning the range $8.6\lt \mathrm{log}({M}_{\star }/{M}_{\odot })\lt 11.5$ . Photometry is decomposed into a central and an outer spatial component using observed z F850LP - H F160W colors. The PROSPECTOR code is used to model spectral energy distributions for the center, outskirt, and integrated galaxy using Hubble Space Telescope/ACS and WFC3, Spitzer/IRAC, and ground-based photometry, with additional constraints on gas-phase metallicity and spectroscopic redshift from MOSDEF spectroscopy. For the low-resolution bands, spatially resolved photometry is determined with an iterative approach. The reconstructed SFHs indicate that the majority of galaxies with $\mathrm{log}({M}_{\star }/{M}_{\odot })\lt 10.5$ are observed while their central regions undergo relatively recent (<100 Myr) bursts of star formation, whereas the outskirts have a smooth, quasi-steady SFH that gently increases toward the redshift of observation. The enhanced star formation activity of the central parts is broadly consistent with the idea that it is produced by highly dissipative gas compaction and accretion. The wide range of central densities and sizes observed in the sample suggests that, for the selected galaxies, such a process has started but is still far from being completed. The implication would be that selecting star-forming galaxies at cosmic noon frequently includes systems in an "evolved" evolutionary phase where the centers have recently started a burst of star formation activity that will likely initiate inside-out quenching in the next several hundred million years.

Keywords: galaxy evolution; galaxy formation; spectral energy distribution
THOR 2.0: Major Improvements to the Open-source General Circulation Model

THOR is the first open-source general circulation model (GCM) developed from scratch to study the atmospheres and climates of exoplanets, free from Earth- or solar-system-centric tunings. It solves the general nonhydrostatic Euler equations (instead of the primitive equations) on a sphere using the icosahedral grid. In the current study, we report major upgrades to THOR, building on the work of Mendonça et al. First, while the horizontally explicit and vertically implicit integration scheme is the same as that described in Mendonça et al., we provide a clearer description of the scheme and improve its implementation in the code. The differences in implementation between the hydrostatic shallow, quasi-hydrostatic deep, and nonhydrostatic deep treatments are fully detailed. Second, standard physics modules are added: two-stream, double-gray radiative transfer and dry convective adjustment. Third, THOR is tested on additional benchmarks: tidally locked Earth, deep hot Jupiter, acoustic wave, and gravity wave. Fourth, we report that differences between the hydrostatic and nonhydrostatic simulations are negligible in the Earth case but pronounced in the hot Jupiter case. Finally, the effects of the so-called "sponge layer," a form of drag implemented in most GCMs to provide numerical stability, are examined. Overall, these upgrades have improved the flexibility, user-friendliness, and stability of THOR.

Keywords: exoplanet atmospheres; exoplanets; hot jupiters; extrasolar rocky planets; astronomy software; atmospheric circulation; open source software; gpu computing
Tracking the X-Ray Polarization of the Black Hole Transient Swift J1727.8–1613 during a State Transition

We report on an observational campaign on the bright black hole (BH) X-ray binary Swift J1727.8–1613 centered around five observations by the Imaging X-ray Polarimetry Explorer. These observations track for the first time the evolution of the X-ray polarization of a BH X-ray binary across a hard to soft state transition. The 2–8 keV polarization degree decreased from ∼4% to ∼3% across the five observations, but the polarization angle remained oriented in the north–south direction throughout. Based on observations with the Australia Telescope Compact Array, we find that the intrinsic 7.25 GHz radio polarization aligns with the X-ray polarization. Assuming the radio polarization aligns with the jet direction (which can be tested in the future with higher-spatial-resolution images of the jet), our results imply that the X-ray corona is extended in the disk plane, rather than along the jet axis, for the entire hard intermediate state. This in turn implies that the long (≳10 ms) soft lags that we measure with the Neutron star Interior Composition ExploreR are dominated by processes other than pure light-crossing delays. Moreover, we find that the evolution of the soft lag amplitude with spectral state does not follow the trend seen for other sources, implying that Swift J1727.8–1613 is a member of a hitherto undersampled subpopulation.

Keywords: accretion; x-ray astronomy; low-mass x-ray binary stars; polarimetry; astrophysical black holes
Direct Evidence of Electron Acceleration at the Dipolarization Front

The dramatic changes in the magnetic field at the dipolarization front (DF) provide a suitable environment for electron acceleration, which usually can cause the flux enhancement of energetic electrons behind the front. However, it is unknown whether energetic electrons observed at the DF are energized locally, and which mechanism accelerates the electrons at the DF is unclear. Our study performs a direct quantitative analysis to reveal the acceleration process of energetic electrons at the DF using the high-time-resolution data from NASA's Magnetospheric Multiscale mission. The fluxes of energetic electrons at 90° are enhanced at the front. Under adiabatic conditions, our quantitative analysis indicates that these electrons at the front could be locally accelerated to over 100 keV by betatron acceleration. Eventually, the electron temperature anisotropy formed via the betatron mechanism could provide the free energy to excite whistler waves at the DF. Our quantitative study provides, for the first time, strong direct evidence for the local electron acceleration at the DF.

Keywords: planetary magnetospheres; space plasmas; plasma physics; plasma jets
Observations of Nonthermal Velocities and Comparisons with an Alfvén Wave Turbulence Model in Solar Active Regions

We present a study of spectral line width measurements from the Extreme-ultraviolet Imaging Spectrometer on Hinode. We used spectral line profiles of Fe XVI 262.984 Å, Fe XIV 264.787 Å, Fe XIV 270.519 Å, Fe XIV 274.203 Å, and Fe XV 284.160 Å, and studied 11 active regions. Previous studies of spectral line widths have shown that in hot loops in the cores of active regions, the observed nonthermal velocities are smaller than predicted from models of reconnection jets in the corona or shock heating associated with Alfvén waves. The observed line widths are also inconsistent with models of chromospheric evaporation due to coronal nanoflares. We show that recent advances in higher resolution Alfvén wave turbulence modeling enables us to obtain nonthermal velocities similar to those measured in active regions. The observed nonthermal velocities for the 11 active regions in our study are in the range of 17–30 km s‑1, consistent with the spectral line nonthermal widths predicted from our model of 16 interacting flux tubes, which are in the range of 15–37 km s‑1.

Keywords: solar physics; solar coronal heating; the sun; solar corona; solar atmosphere
A Study of 90 GHz Dust Emissivity on Molecular Cloud and Filament Scales

Recent observations from the MUSTANG2 instrument on the Green Bank Telescope have revealed evidence of enhanced long-wavelength emission in the dust spectral energy distribution (SED) in the Orion Molecular Cloud (OMC) 2/3 filament on 25″ (0.1 pc) scales. Here we present a measurement of the SED on larger spatial scales (map size 0.°5-3° or 3-20 pc), at somewhat lower resolution (120″, corresponding to 0.25 pc at 400 pc) using data from the Herschel satellite and Atacama Cosmology Telescope (ACT). We then extend the 120″-scale investigation to other regions covered in the Herschel Gould Belt Survey (HGBS), specifically the dense filaments in the southerly regions of Orion A, Orion B, and Serpens-S. Our data set in aggregate covers approximately 10 deg2, with continuum photometry spanning from 160 μm to 3 mm. These OMC 2/3 data display excess emission at 3 mm, though less (10.9% excess) than what is seen at higher resolution. Strikingly, we find that the enhancement is present even more strongly in the other filaments we targeted, with an average excess of 42.4% and 30/46 slices showing an inconsistency with the modified blackbody to at least 4σ. Applying this analysis to the other targeted regions, we lay the groundwork for future high-resolution analyses. Additionally, we also consider a two-component dust model motivated by Planck results and an amorphous grain dust model. While both of these have been proposed to explain deviations in emission from a generic modified blackbody, we find that they have significant drawbacks, requiring many spectral points or lacking experimental data coverage.

Keywords: star formation; protostars; interstellar dust; molecular clouds
Gas Dynamics of the Nickel-56 Decay Heating in Pair-instability Supernovae

Very massive 140-260 M⊙ stars can die as highly energetic pair-instability supernovae (PI SNe) with energies of up to 100 times those of core-collapse SNe that can completely destroy the star, leaving no compact remnant behind. These explosions can synthesize 0.1-30 M⊙ of radioactive 56Ni, which can cause them to rebrighten at later times when photons due to 56Ni decay diffuse out of the ejecta. However, heat from the decay of such large masses of 56Ni could also drive important dynamical effects deep in the ejecta that are capable of mixing elements and affecting the observational signatures of these events. We have now investigated the dynamical effect of 56Ni heating on PI SN ejecta with high-resolution two-dimensional hydrodynamic simulations performed with the CASTRO code. We find that expansion of the hot 56Ni bubble forms a shell at the base of the silicon layer of the ejecta ∼200 days after the explosion but that no hydrodynamical instabilities develop that would mix 56Ni with the 28Si/16O-rich ejecta. However, while the dynamical effects of 56Ni heating may be weak they could affect the observational signatures of some PI SNe by diverting decay energy into internal expansion of the ejecta at the expense of rebrightening at later times.

Keywords: supernova dynamics; nuclear astrophysics; supernovae; astrophysical fluid dynamics; population iii stars; hypernovae; massive stars; astrophysical explosive burning; hydrodynamical simulations; shocks
The Absolute Age of M92

The absolute age of a simple stellar population is of fundamental interest for a wide range of applications but is difficult to measure in practice, as it requires an understanding of the uncertainties in a variety of stellar evolution processes as well as the uncertainty in the distance, reddening, and composition. As a result, most studies focus only on the relative age by assuming that stellar evolution calculations are accurate and using age determinations techniques that are relatively independent of distance and reddening. Here, we construct 20,000 sets of theoretical isochrones through Monte Carlo simulation using the Dartmouth Stellar Evolution Program to measure the absolute age of the globular cluster M92. For each model, we vary a range of input physics used in the stellar evolution models, including opacities, nuclear reaction rates, diffusion coefficients, atmospheric boundary conditions, helium abundance, and treatment of convection. We also explore variations in the distance and reddening as well as its overall metallicity and α enhancement. We generate simulated Hess diagrams around the main-sequence turn-off region from each set of isochrones and use a Voronoi binning method to fit the diagrams to Hubble Space Telescope Advanced Camera for Surveys data. We find the age of M92 to be 13.80 ± 0.75 Gyr. The 5.4% error in the absolute age is dominated by the uncertainty in the distance to M92 (~80% of the error budget); of the remaining parameters, only the total metallicity, α element abundance, and treatment of helium diffusion contribute significantly to the total error.

Keywords: globular star clusters; stellar physics; computational astronomy; stellar evolutionary models
Evidence of Accretion Burst: The Viscously Heated Inner Disk of the Embedded Protostar IRAS 16316-1540

Outbursts of young stellar objects occur when the mass accretion rate suddenly increases. However, such outbursts are difficult to detect for deeply embedded protostars due to their thick envelope and the rarity of outbursts. The near-IR spectroscopy is a useful tool to identify ongoing outburst candidates by the characteristic absorption features that indicate a disk origin. However, without high-resolution spectroscopy, the spectra of outburst candidates can be confused with the late-type stars since they have similar spectral features. For the protostar IRAS 16316-1540, the near-IR spectrum has line equivalent widths that are consistent with M-dwarf photospheres. However, our high-resolution IGRINS spectra reveal that the absorption lines have boxy and/or double-peaked profiles, as expected from a disk and not the star. The continuum emission source is likely the hot, optically thick disk, heated by viscous accretion. The projected disk rotation velocity of 41 ± 5 km s-1 corresponds to ~0.1 au. Based on the result, we suggest IRAS 16316-1540 as an ongoing outburst candidate. Viscous heating of disks is usually interpreted as evidence for ongoing bursts, which may be more common than previously estimated from low-resolution near-IR spectra.

Keywords: protostars; protoplanetary disks; young stellar objects; high resolution spectroscopy
Evidence of Electron Acceleration via Nonlinear Resonant Interactions with Whistler-mode Waves at Foreshock Transients

Shock waves are sites of intense plasma heating and charged particle acceleration. In collisionless solar wind plasmas, such acceleration is attributed to shock drift or Fermi acceleration but also to wave-particle resonant interactions. We examine the latter for the case of electrons interacting with one of the most commonly observed wave modes in shock environments, the whistler mode. Such waves are particularly intense in dynamic, localized regions upstream of shocks, arising from the kinetic interaction of the shock with solar wind discontinuities. These regions, known as foreshock transients, are also sites of significant electron acceleration by mechanisms not fully understood. Using in situ observations of such transients in the Earth's foreshock, we demonstrate that intense whistler-mode waves can resonate nonlinearly with >25 eV solar wind electrons and accelerate them to ~100-500 eV. This acceleration is mostly effective for the 50-250 eV energy range, where the accelerated electron population exhibits a characteristic butterfly pitch-angle distribution consistent with theoretical predictions. Such nonlinear resonant acceleration is very fast, implying that this mechanism may be important for injecting suprathermal electrons of solar wind origin into the shock region, where they can undergo further, efficient shock-drift acceleration to even higher energies.

Keywords: planetary bow shocks
A Phenomenon Resembling Early Superhumps in a New SU UMa-type Dwarf Nova with a 2 hr Orbital Period

We investigate K2BS5, an optical transient that we identified in Campaign 13 of the Kepler/K2 archives by the K2 Background Survey, and classify it as a new SU UMa-type dwarf nova. Using the light curve generated from Keplers long-cadence observation mode, we analyze the dwarf nova during quiescence and superoutburst. Following 20 days of quiescence at the start of the observation, the system entered a superoutburst lasting 12 days, after which it experienced at least one rebrightening. K2BS5 clearly meets the criteria for an SU UMa star, but at the peak of the superoutburst, it also shows double-wave oscillations consistent with the spectroscopic orbital period, a phenomenon that closely resembles early superhumps in WZ Sge stars. While we do not classify K2BS5 as a WZ Sge system, we discuss how this phenomenon could complicate efforts to use the suspected detection of early superhumps to distinguish SU UMa-type dwarf novae from the recently recognized class of long-orbital-period WZ Sge systems.

Keywords: cataclysmic variable stars; wz sagittae stars; dwarf novae; su ursae majoris stars; stellar accretion disks; stellar accretion; late stellar evolution
An Update on the Future Flyby of Gliese 710 to the Solar System Using Gaia DR3: Flyby Parameters Reproduced, Uncertainties Reduced

Charting the near-future motion of known stars through the galaxy, none will pass closer to the Sun than Gliese 710. Here, we present an updated analysis of this upcoming flyby using Gaia DR3 data as well as the latest planetary ephemerides. Our new estimate reproduces the nominal values of those already published, but with reduced associated uncertainties. The distribution of distances of closest approach has a median value of 0.052 pc with a 90% probability of coming within 0.048-0.056 pc of the Sun; the associated time of perihelion passage is determined to be between 1.26 and 1.33 Myr with 90% confidence, with a most likely value of 1.29 Myr.

Keywords: stellar kinematics; solar neighborhood; solar system
Spectral Signatures of Quasar Ages at z ≈ 3

Insight into quasar ages may be obtained from the proximity effect, but so far only in a limited number of bright quasars. Based on ∼2600 Sloan Digital Sky Survey quasar spectra at 2.5 ≤ z ≤ 3.5, a search for spectral voids between Lyα forest lines finds proximity zones over a wide range of radial distances. The majority of zone sizes are less than 5 Mpc, with their numbers decreasing exponentially toward larger distances. After a normalization by luminosities, the zone sizes are distributed with an e-folding scale of 0.64 as compared with the anticipated values. A group of quasars are selected for their large proximity zones of ≳10 Mpc. Their composite spectrum displays strong narrow cores and large equivalent widths in Lyα and other major UV emission lines. If the proximity zones along lines of sight are indicative of quasar ages, these features may be the signatures of old quasars. Another group of quasars are selected as they show no proximity zone and exhibit intrinsic absorption lines at zab > zem. They are likely young quasars and exhibit weaker narrow emission-line components. The significant difference of spectral features between the two groups may reflect an evolution pattern over quasars' lifetimes.

Keywords: quasars
Is the Large-scale Structure Traced by the BOSS LOWZ Galaxies Consistent with Planck?

Recently, several studies reported a significant discrepancy between the clustering and lensing of the Baryon Oscillation Spectroscopic Survey (BOSS) galaxies in the Planck cosmology. We construct a simple yet powerful model based on the linear theory to assess whether this discrepancy points toward deviations from Planck. Focusing on scales 10 < R < 30 h -1Mpc, we model the amplitudes of clustering and lensing of BOSS LOWZ galaxies using three parameters: galaxy bias b g; galaxy-matter cross-correlation coefficient r gm; and A, defined as the ratio between the true and Planck values of σ 8. Using the cross-correlation matrix as a diagnostic, we detect systematic uncertainties that drive spurious correlations among the low-mass galaxies. After building a clean LOWZ sample with r gm ~ 1, we derive a joint constraint of b g and A from clustering+lensing, yielding ${b}_{{\rm{g}}}={2.47}_{-0.30}^{+0.36}$ and $A={0.81}_{-0.09}^{+0.10}$ , i.e., a 2σ tension with Planck. However, due to the strong degeneracy between b g and A, systematic uncertainties in b g could masquerade as a tension with A = 1. To ascertain this possibility, we develop a new method to measure b g from the cluster-galaxy cross correlation and cluster weak lensing using an overlapping cluster sample. By applying the independent bias measurement (b g = 1.76 ± 0.22) as a prior, we successfully break the degeneracy and derive stringent constraints of ${b}_{{\rm{g}}}={2.02}_{-0.15}^{+0.16}$ and A = 0.96 ± 0.07. Therefore, our result suggests that the large-scale clustering and lensing of LOWZ galaxies are consistent with Planck, while the different bias estimates may be related to some observational systematics that need to be mitigated in future surveys.

Keywords: cosmological parameters from large-scale structure; sigma8; observational cosmology; large-scale structure of the universe; weak gravitational lensing; dark matter; cosmology
Is Solar Minimum 24/25 Another Unusual One?

Solar minimum 23/24 is considered to be unusual because it exhibits features that differ notably from those commonly seen in previous minima. In this Letter, we analyze the solar polar magnetic field, the potential-field solution of the solar corona, and the in situ solar wind measurements to see if the recent solar minimum 24/25 is another unusual one. While the dipolar configuration that is commonly seen during minimum 22/23 and earlier minima persist for about half a year after the absolute minimum of solar cycle 24, the corona has a morphology that is more complex than a simple dipole before the absolute minimum. The fast solar wind streams are less dominant than minimum 23/24. The interplanetary magnetic field strength, density, and mass flux that are historically low in the minimum 23/24 are regained during minimum 24/25, but still do not reach the minimum 22/23 level. From the analysis of this Letter, it seems that the minimum 24/25 is only partly unusual, and the recovery of the commonly minimum features may result from the enhancement of the polar field.

Keywords: solar cycle; solar wind; solar corona; interplanetary magnetic fields