Sazuna/UAT_keywords huggingface dataset:
New Near-infrared Coronal Lines Observed during the 2019 Total Solar Eclipse. We report on a further analysis of the Airborne Infrared Spectrometer (AIR-Spec) observations from the 2019 July 2 total eclipse and present the identifications of three new coronal lines from Fe X, Si XI, and Si VI in AIR-Spec's 1.87–1.99 μm band. The new lines were predicted to be observable but were not observed previously in the corona. The identifications are confirmed on the basis of observed and expected line wavelengths and radiances. The observed wavelengths are very accurate, as confirmed by neutral H and He lines measured during the same observation. The predicted wavelengths are assessed by reviewing previous experimental data used to estimate the energies of these ions. We find discrepancies with several previous measurements. A reanalysis of Solar Ultraviolet Measurement of Emitted Radiation data corrects previous measurements and provides excellent agreement with the AIR-Spec values for Si XI. AIR-Spec was developed to survey the near-infrared (NIR) coronal spectrum from above Earth's atmosphere, a critical first step in designing future balloonborne and spaceborne instrumentation to observe coronal plasma and magnetic fields using NIR emission lines. The reported results are also of interest for ground-based observatories, as the precise measurements of line wavelength enable observers to understand the nearby telluric spectrum and determine which lines can be used from the ground.

Keywords: Solar coronal lines, Spectrometers, Total eclipses, Solar instruments
Thermal Electrons in the Radio Afterglow of Relativistic Tidal Disruption Event ZTF22aaajecp/AT 2022cmc. A tidal disruption event (TDE) occurs when a star travels too close to a supermassive black hole. In some cases, accretion of the disrupted material onto the black hole launches a relativistic jet. In this paper, we present a long-term observing campaign to study the radio and submillimeter emission associated with the fifth jetted/relativistic TDE: AT 2022cmc. Our campaign reveals a long-lived counterpart. We fit three different models to our data: a nonthermal jet, a spherical outflow consisting of both thermal and nonthermal electrons, and a jet with thermal and nonthermal electrons. We find that the data are best described by a relativistic spherical outflow propagating into an environment with a density profile following R−1.8. Comparison of AT 2022cmc to other TDEs finds agreement in the density profile of the environment but also that AT 2022cmc is twice as energetic as the other well-studied relativistic TDE, Swift J1644. Our observations of AT 2022cmc allow a thermal electron population to be inferred for the first time in a jetted transient, providing new insights into the microphysics of relativistic transients jets.

Keywords: Tidal disruption, Jets, Radio transient sources
Bondi-like Accretion Flow Dynamics: The Role of Gravitational Potential. The formation of massive black holes and their coevolution with host galaxies are pivotal areas of modern astrophysics. Spherical accretion onto a central point mass serves as a foundational framework in cosmological simulations, semi-analytical models, and observational studies. In this paper, we extend the classical spherical accretion model by incorporating the gravitational potential of host galaxies, including contributions from stellar components and dark matter (DM) halos. Numerical solutions spanning scales from parsecs down to ∼10 rs reveal that the flow structure is highly sensitive to the mass and size of the DM halo. Adding a small amount of angular momentum to the accreting gas demonstrates that such flows resemble spherical Bondi accretion, with mass accretion rates converging toward the Bondi rate. We find that the low angular momentum flow resembles the spherical Bondi flow, and its mass accretion rate approaches the Bondi accretion rate. Remarkably, due to the presence of DM, the mass accretion rate increases by more than ∼100% compared to analogous hydrodynamic solutions without DM. These findings underscore the critical role of stellar and DM gravitational potentials in shaping the dynamics and accretion rates of quasi-spherical flows, providing new insights into astrophysical accretion processes.

Keywords: Accretion, Black holes, Hydrodynamics, Bondi accretion, Active galactic nuclei, Dark matter
Tracing Magnetic Field in Super-Alfvénic Turbulence with Gradient Technique. Super-Alfvénic turbulence is important for many astrophysical objects, particularly galaxy clusters. In this paper, we explore the accuracy of synchrotron intensity gradients and X-ray intensity gradients to map magnetic fields in super-Alfvénic turbulence for a set of astrophysically relevant parameters of turbulent driving. Analyzing our synthetic observations, we report a good accuracy for both techniques. Our results are suggestive that other types of gradient technique can be successfully employed to trace magnetic fields within super-Alfvénic subsonic turbulence.

Keywords: Interstellar magnetic fields, Interstellar medium
On the Eddington Capture Surface around Spherically Symmetric Compact Objects with Separable Luminosity Distributions. Radiation exerts pressure, and therefore it is possible for an intensely bright object to balance the gravitational force near a massive compact object. General relativity demonstrates that this balance occurs for super-Eddington luminosities at a finite distance from the center of the mass. These equilibrium positions are referred to as Eddington capture surfaces (ECSs). At the ECSs, particles can collect in a thin shell, balanced between the inward curvature of spacetime and the outward flow of radiation. We adopt spherical symmetry but otherwise leave the metric functions generalized. This approach allows us to study the ECSs under the effect of arbitrary spherically symmetric metrics. We adopt a separable luminosity function that depends on both the radial direction and the angular coordinates over the surface of the star. We demonstrate that the morphology of an ECS varies depending on the angular luminosity distribution and can even split into multiple, separate, disconnected equilibrium surfaces. The ECS phenomenon is closely related to type I photospheric radius expansion X-ray bursts.

Keywords: Neutron stars, Black holes, Ultraluminous x-ray sources, General relativity, X-ray bursts
White Dwarfs with Infrared Excess in the HET Dark Energy Experiment. White dwarfs with infrared excess emission provide a window into the late stages of stellar evolution and the dynamics of circumstellar environments. Using data from the Hobby–Eberly Telescope Dark Energy Experiment, we characterized 30 white dwarfs exhibiting infrared excess, including 29 DA and 1 DB stars. While an infrared excess can arise from dusty disks or cool (sub)stellar companions, our sample is limited to stellar companions, due to our selection based on SDSS photometry, which is sensitive to excess emission at wavelengths λ &lt; 1 μm. Our sample contains 22 newly identified excess sources not previously reported in the literature. Spectroscopic observations are available for 10 sources via SDSS, of which only 8 have prior spectroscopic classifications in the literature. In this paper, we present the determination of the effective temperature and surface gravity of these white dwarfs. We used the Balmer line profiles to compare with current atmospheric models in order to determine the photospheric parameters of the white dwarfs, minimizing contamination introduced by the infrared source. We used photometric data from the SDSS and the Gaia mission to resolve the degeneracies between hot and cold solutions from spectroscopy, constraining the photospheric parameters. These results help refine our understanding of white dwarf evolution in binary systems, focusing on stellar companions that cause the infrared excess. This study contributes to identifying systems with potential substellar companions or unresolved stellar partners, adding to the growing effort to map out the fate of planetary systems after their host stars evolve beyond the main sequence.

Keywords: White dwarf stars, Surface gravity, Stellar effective temperatures, Infrared excess, Photometry, Spectroscopy
Hidden Figures of Globular Clusters: Integrated Stellar Populations Impacted by Hot Subdwarfs. Globular clusters (GCs) are fundamental for understanding the integrated light of old stellar populations and galaxy assembly processes. However, the role of hot, evolved stars, such as horizontal branch (HB), extreme HB, and blue stragglers, remains poorly constrained. These stars are often underrepresented or entirely excluded from stellar population models, despite their dominant contribution to the ultraviolet (UV) flux. Their presence can bias age estimates by mimicking the spectral signatures of younger populations. We examined the impact of evolved hot stars on the models using two well-studied Galactic GCs with high-quality Hubble Space Telescope photometry and integrated spectra from the International Ultraviolet Explorer and the Blanco Telescope. NGC 2808 and NGC 7089 (M 2) have extended HBs and are proxies for old stellar populations. Integrated spectra were constructed using a color magnitude diagram─based (CMD-based) method, matching observed stars to evolutionary phases and then to appropriate synthetic stellar libraries, enabling the HB morphology to be taken into account. Our findings show that the inclusion of evolved hot stars significantly improves the agreement between the model and observed spectra from the UV to the optical. The inclusion of these phases reduced the residuals in spectral comparisons. Our results reinforce that comprehensive stellar population models incorporating evolved hot components are essential to accurately date unresolved systems and to robustly trace formation histories of extragalactic galaxies.

Keywords: Globular star clusters, Horizontal branch, Multi-color photometry, Subdwarf stars, Stellar populations, Spectral energy distribution
GWSkyNet-Multi. II. An Updated Machine Learning Model for Rapid Classification of Gravitational-wave Events. Multimessenger observations of gravitational waves and electromagnetic emission from compact object mergers offer unique insights into the structure of neutron stars, the formation of heavy elements, and the expansion rate of the Universe. With the LIGO–Virgo–KAGRA (LVK) gravitational-wave detectors currently in their fourth observing run (O4), it is an exciting time for detecting these mergers. However, assessing whether to follow up a candidate gravitational-wave event given limited telescope time and resources is challenging; the candidate can be a false alert due to detector glitches, or may not have any detectable electromagnetic counterpart even if it is real. GWSkyNet-Multi is a machine learning model developed to facilitate follow-up decisions by providing real-time classification of candidate events, using localization information released in LVK rapid public alerts. Here we introduce GWSkyNet-Multi II, an updated model targeted toward providing more robust and informative predictions during O4 and beyond. Specifically, the model now provides normalized probability scores and associated uncertainties for each of the four corresponding source categories released by the LVK: glitch, binary black hole, neutron star–black hole, and binary neutron star. Informed by explainability studies of the original model, the updated model architecture is also significantly simplified, including replacing input images with intuitive summary values that are more interpretable. For significant event alerts issued during O4a and O4b, GWSkyNet-Multi II produces a prediction that is consistent with the updated LVK classification for 93% of events. The updated model can be used by the community to help make time-critical follow-up decisions.

Keywords: Gravitational wave astronomy, Gravitational wave sources, Neural networks
QZO: A Catalog of 5 Million Quasars from the Zwicky Transient Facility. Machine learning methods are well established in the classification of quasars (QSOs). However, the advent of light-curve observations adds a great amount of complexity to the problem. Our goal is to use the Zwicky Transient Facility (ZTF) to create a catalog of QSOs. We process the ZTF DR20 light curves with a transformer artificial neural network and combine different surveys with extreme gradient boosting. Based on ZTF g-band and Wide-field Infrared Survey Explorer (WISE) observations, we find 4,849,574 objects classified as QSOs with confidence higher than 90% (QZO). We robustly classify objects fainter than the 5σ signal-to-noise ratio (SNR) limit at g = 20.8 by requiring g &lt; nobs/80 + 20.375. For 33% of QZO objects, with available WISE data, we publish redshifts with estimated error Δz/(1 + z) = 0.14. We find that ZTF classification is superior to the Pan-STARRS static bands, and on par with WISE and Gaia measurements, but the light curves provide the most important features for QSO classification in the ZTF data set. Using ZTF g-band data with at least 100 observational epochs per light curve, we obtain a 97% F1 score for QSOs. We find that with 3 day median cadence, a survey time span of at least 900 days is required to achieve a 90% QSO F1 score. However, one can obtain the same score with a survey time span of 1800 days and the median cadence prolonged to 12 days.

Keywords: Astroinformatics, Light curve classification , Classification, Quasars, Neural networks, Large-scale structure of the universe, Light curves, Time series analysis, Active galactic nuclei, Time domain astronomy, Photometry, Catalogs
Tidal Heating in Detached Double White Dwarf Binaries. Short-period (P &lt; 1 hr orbits) detached double white dwarf binary (DWDB) components identified with transient surveys (e.g., SDSS, Zwicky Transient Facility, hereafter ZTF) have hot surface temperatures (&gt;10,000 K) and observed radii a factor of 2 larger than completely degenerate white dwarfs. We formulate tidal heating in helium composition, extremely low-mass white dwarf components of detached DWDBs, which reach mass transfer within a Hubble time. We combine a mass─radius relation that varies with surface temperature and the equilibrium tidal friction model of Hut 1981, where the additional orbital energy loss from tidal friction is accounted for by increases in the primary surface temperature, and hence increasing radius. Applying this heating model to the current sample of binaries with ZTF, we predict temperature increases from the present day of up to ∼40% before the onset of mass transfer. We find that helium white dwarfs are generically hot and large at the onset of mass transfer, even for the oldest DWDBs whose components can cool to be degenerate by the present day. In the population of Galactic DWDBs, we find that the onset of mass transfer should occur at orbital periods as long as 1000 s (17 minutes), or binary gravitational-wave frequency of 2 mHz. This is over 3 times longer than periods expected for degenerate white dwarfs (5 minutes). Since mass transferring DWDBs are progenitors for a variety of transients and stellar populations, e.g., RCrB stars, AM CVn binaries, so-called Type .Ia supernova, the finite temperature of donor white dwarfs should be taken into account.

Keywords: Close binary stars, Tidal friction, White dwarf stars
The Parallel Ionizing Emissivity Survey (PIE). I. Survey Design and Selection of Candidate Lyman Continuum Leakers at 3.1 &lt; z &lt; 3.5. We present the survey design and initial results from the Parallel Ionizing Emissivity (PIE) survey. PIE is a large Hubble Space Telescope survey designed to detect Lyman continuum (LyC) emitting galaxies at 3.1 &lt; z &lt; 3.5 and stack their images in order to measure average LyC escape fractions as a function of galaxy properties. PIE has imaged 37 independent fields in three filters (F336W, F625W, and F814W), of which 18 are observed with a fourth band (F475W) from the accompanying PIE+ program. We use photometric colors to select candidate Lyman break galaxies (LBGs) at 3.1 &lt; z &lt; 3.5, which can be followed up using ground-based spectrographs to confirm their redshifts. Unlike previous surveys, we use many independent fields to remove biases caused by correlated absorption in the intergalactic medium (IGM). In this paper, we describe the survey design, photometric measurements, and the use of mock galaxy samples to optimize our color selection. With three filters, we can select a galaxy sample of which ≍90% are LBGs and over 30% lie in the 3.1 &lt; z &lt; 3.5 range for which we can detect uncontaminated LyC emission in F336W. We also use mock IGM sight lines to measure the expected transmission of the IGM, which will allow us to determine escape fractions from our stacked galaxies. We color-select ≍1400 galaxies, and predict that this includes ≍80 LyC-emitting galaxies and ≍500 that we can use in stacking. Finally, we present the Keck/LRIS spectrum of a galaxy at z ≍ 2.99, demonstrating that we can confirm the redshifts of z ∼ 3 galaxies from the ground.

Keywords: Lyman-break galaxies, Galaxy photometry, Reionization, Galaxy spectroscopy, Galaxies
HAWC Performance Enhanced by Machine Learning in Gamma-hadron Separation. Improving gamma-hadron separation is one of the most effective ways to enhance the performance of ground-based gamma-ray observatories. With more than a decade of continuous operation, the High-Altitude Water Cherenkov (HAWC) Observatory has contributed significantly to high-energy astrophysics. To further leverage its rich data set, we introduce a machine learning approach for gamma-hadron separation. A multilayer perceptron shows the best performance, surpassing traditional and other machine learning–based methods. This approach shows a notable improvement in the detector's sensitivity, supported by results from both simulated and real HAWC data. In particular, it achieves a 19% increase in significance for the Crab Nebula, commonly used as a benchmark. These improvements highlight the potential of machine learning to significantly enhance the performance of HAWC and provide a valuable reference for ground-based observatories, such as the Large High Altitude Air Shower Observatory and the upcoming Southern Wide-field Gamma-ray Observatory.

Keywords: Classification, Neural networks, Multivariate analysis, Gamma-rays, Cosmic rays
Lopsided and Bulging Distribution of Satellites Around Paired Halos. I. Observational Measurements and Comparison with Halo-based Models. We investigate the angular distribution of satellite galaxies in and around pairs of galaxy groups in the Sloan Digital Sky Survey (SDSS) and compare the results with the satellite distribution in pairs of dark matter halos by constructing mock catalogs that account for the same selection effects as the observational sample. We find that the angular distribution of satellites in both SDSS and the mock catalog exhibits a pronounced tendency toward lopsidedness, with satellites preferentially located between the two central galaxies. Additionally, there is a significant bulging distribution characterized by a higher concentration of satellites along the line connecting the two centrals compared to those found perpendicular to it. The lopsided and bulging distributions strengthen as pair separation and halo mass increase. The mock catalog successfully reproduces the observational results across all cases considered. We find that the lopsided and bulging distribution of satellites can largely be explained by overlapping two randomly selected halos matched in mass to the actual halo pairs, along with their surrounding satellite distribution, provided that the alignment between the orientations of the halos and the line connecting the halo pairs is taken into account. This suggests that the angular distribution of satellites is a natural consequence of the formation and evolution of large-scale structure in a Λ cold dark matter universe, eliminating the need to introduce other physical origins.

Keywords: Galaxy dark matter halos, Galaxy pairs, Galaxy evolution, Large-scale structure of the universe
TiDES: The 4MOST Time Domain Extragalactic Survey. The Time Domain Extragalactic Survey (TiDES) conducted on the 4 m Multi-Object Spectroscopic Telescope will perform spectroscopic follow-up of extragalactic transients discovered in the era of the NSF-DOE Vera C. Rubin Observatory. TiDES will conduct a 5 yr survey, covering  &gt;14,000squaredegrees , and use around 250,000 fibre hours to address three main science goals: (i) spectroscopic observations of &gt;30,000 live transients, (ii) comprehensive follow-up of &gt;200,000 host galaxies to obtain redshift measurements, and (iii) repeat spectroscopic observations of active galactic nuclei to enable reverberation mapping studies. The live spectra from TiDES will be used to reveal the diversity and astrophysics of both normal and exotic supernovae across the luminosity-timescale plane. The extensive host-galaxy redshift campaign will allow exploitation of the larger sample of supernovae and improve photometric classification, providing the largest-ever sample of SNe Ia, capable of a sub-2% measurement of the equation-of-state of dark energy. Finally, the TiDES reverberation mapping experiment of 700–1000 AGN will complement the SN Ia sample and extend the Hubble diagram to z ∼ 2.5.

Keywords: Cosmology, Surveys, Active galaxies, Astronomy data analysis, Supernovae, Redshift surveys
Impulsive Mixing of Stellar Populations in Dwarf Spheroidal Galaxies. We study the response of mono-energetic stellar populations with initially isotropic kinematics to impulsive and adiabatic changes to an underlying dark matter potential. Half-light radii expand and velocity dispersions decrease as enclosed dark matter is removed. The details of this expansion and cooling depend on the timescale on which the underlying potential changes. In the adiabatic regime, the product of half-light radius and average velocity dispersion is conserved. We show that the stellar populations maintain centrally isotropic kinematics throughout their adiabatic evolution, and their densities can be approximated by a family of analytical radial profiles. Metallicity gradients within the galaxy flatten as dark matter is slowly removed. In the case of strong impulsive perturbations, stellar populations develop power-law-like density tails with radially biased kinematics. We show that the distribution of stellar binding energies within the dark matter halo substantially widens after an impulsive perturbation, no matter the sign of the perturbation. This allows initially energetically separated stellar populations to mix, to the extent that previously chemo-dynamically distinct populations may masquerade as a single population with large metallicity and energy spread. Finally, we show that in response to an impulsive perturbation, stellar populations that are deeply embedded in cored dark matter halos undergo a series of damped oscillations before reaching a virialized equilibrium state, driven by inefficient phase mixing in the harmonic potentials of cored halos. This slow return to equilibrium adds substantial systematic uncertainty to dynamical masses estimated from Jeans modeling or the virial theorem.

Keywords: Galaxy dynamics, Cold dark matter, Dwarf spheroidal galaxies, Perturbation methods, N-body simulations