Sazuna/UAT_keywords huggingface dataset:
A Selection of 23 Bright Hypervelocity Gaia DR3 Stars. From the Gaia DR3 data twenty three bright hypervelocity stars that have Tycho catalogue numbers are presented. All these stars are of high galactic latitude and some may be galactic halo stars. All of them have accurate Gaia DR3 parallaxes and radial velocities. There is hardly any relevant literature on some of these stars. The Gaia DR3 astrophysical parameters of some of these stars indicate that they are of late spectral types and some are metal-poor. The astrophysical parameters are available for some of these stars in the literature but they differ from the Gaia DR3 results. Detailed chemical composition determination of these stars from an analysis of high resolution spectra is very much needed to further understand the evolutionary status and how these stars acquired such high radial velocities.

Keywords: Hypervelocity stars
CO and C I Emission in the Early Spectrum of the Nova V1391 Cassiopeiae. V1391 Cassiopeiae is one of a growing number of novae to show emission from carbon monoxide but only the second to display molecular absorption as well (after V2676 Ophiuchi). In this Research Note, we present a 0.69–5.2 μm spectrum that includes both the CO fundamental and first overtone as well as a prominent, very low ionization spectrum dominated by the lines of C I. Relative to the CO first overtone, the CO fundamental is a factor of ten weaker than expected if the emission were optically thin. Modeling of the spectral structure of the first overtone indicates a CO temperature of 4000 K and 13C/12C of 0.5. CO emission coexisted with strong C I and O I emission so carbon monoxide formation did not fully incorporate either of the constituent elements.

Keywords: Classical novae
Variability Census of Legacy Catalogs. II. 6600+ New δ Scuti and γ Doradus Stars. From Phase II of a variability vetting census in BD, HD, SAO and PPM catalogs, I have identified a total of new variables of over 5000 δ Scuti, 3500 γ Doradus, 1200 Maia variables, 4 RR Lyrae stars, 420 eclipsing binaries, 5500 rotating variables (220+ ellipsoidal variable stars, 550+ ACV and several other subtypes including solar-like oscillators), and other types. Notably, more than 66 eclipsing binary systems have been identified with pulsating primary components of either DSCT or GDOR type, while 10 more binaries feature overlapping Maia-type pulsation. Moreover, over 960 of these variables exhibit hybrid δ Sct-γ Dor pulsations. *Dedicated to my wife Jingyun Zhang.

Keywords: Delta Scuti variable stars, Pulsating variable stars, RR Lyrae variable stars, Eclipsing binary stars, Gamma Doradus variable stars
Classifying Emission-line Galaxies Using a Dense Neural Network and Support Vector Machine. In this study we present an innovative approach to classifying emission-line galaxies, specifically categorizing them as Star-forming, Seyfert, Low Ionization Nuclear Emission Line Regions, or Composites. Leveraging both a Dense Neural Network and Support Vector Machine, we use key emission-line flux ratios as input features extracted from the Baryon Oscillation Spectroscopic Survey data within the Sloan Digital Sky Survey. The high accuracy in classification for both Machine Learning models showcases their effectiveness and viability in accurately classifying emission-line galaxies with slightly different inputs and target classifications compared to past Machine Learning models.

Keywords: Classification, Neural networks, Support vector machine, Emission line galaxies, Galaxy spectroscopy
Machine Learning-based Classification of Variable Stars. The classification of variable stars, essential for revealing information on stellar properties and cosmic distances, traditionally relied on statistical methods and limited data. With the emergence of transformative machine learning methodologies and large stellar surveys, we are able to perform more efficient, accurate, and robust handling of expansive databases. We deploy two different machine learning models—random forest and XGBoost—that effectively classify variable stars identified in the most recent phase of the Optical Gravitational Lensing Experiment using four features: (1) time of minimum brightness, (2) I-band amplitude, (3) mean or maximum I-band magnitude, and (4) period. The two models achieve a cross-correlation score of 99.00%, indicating largely shared classifications. The results produced by the models uncover new insights into the precision of supervised learning models in predicting variable stars with the aid of the most up-to-date survey data.

Keywords: Delta Scuti variable stars, Classification, Anomalous Cepheid variable stars, Cepheid variable stars, RR Lyrae variable stars, Long period variable stars, Variable stars, Eclipsing binary stars, Random Forests, Intrinsic variable stars
Lopsided Galaxy Distributions in Massive TNG300 Clusters. Studies of isolated central galaxies and their satellites have shown that the spatial distributions of the satellites are distinctly "lopsided" with respect to the locations of the central galaxies. Here we extend this type of analysis to larger systems by analyzing the lopsidedness of 280 massive galaxy clusters in the IllustrisTNG300 Λ Cold Dark Matter simulation. Using a pairwise clustering statistic, we compute the probability that pairs of cluster galaxies are separated by a given polar angle difference, Δϕ, in the plane of the sky. Relative to the location of the central cluster galaxy, we find a statistically significant excess of galaxy pairs that are located on the same side of the cluster. The lopsidedness of the galaxy distribution is most pronounced for large clusters and for pairs of intrinsically red galaxies. The results summarized here were presented at the 243rd meeting of the American Astronomical Society.

Keywords: Cosmology, Cold dark matter, Galaxy clusters
The Selection Function of Gaia DR3 RR Lyrae. The Third Data Release (DR3) of the Gaia mission almost doubled the number of RR Lyrae (RRL) stars release in its Specific Object Studies (SOS) catalog, in comparison with DR2. Here I provide empirically inferred 2D and 3D completeness maps for the Gaia DR3 SOS RRL catalog along with maps for the combined Gaia SOS+PS1+ASAS-SN-II catalog. The latter currently has the best performance with an improvement of 9% relative to Gaia DR3 alone and close to 20% relative to Gaia DR2 for the VC+SOS RRL, while significantly smoothing out the effect of the Gaia scanning law.

Keywords: RR Lyrae variable stars, Astronomy databases
HST Far-ultraviolet Transit Observations of Two Neptune Progenitors Younger than 30 Myr. Photoevaporation is believed to dominate the removal of planetary atmospheres when they are young (&lt;100 Myr). Signatures of atmospheric mass-loss can be observed in the ultraviolet (UV) through the near-infrared. We present Far-UV transit observations of AU Mic b (∼22 Myr) and V1298 Tau c (∼28 Myr) with the Hubble Space Telescope. We search for evidence of escaping metals in the C II, Si II, and Si III emission lines and compare their behavior to tracers of stellar activity. We detect no evidence of atmospheric mass loss, and place upper limits on the radii of AU Mic b and V1298 Tau c.

Keywords: Atmospheric evolution, Transits, Ultraviolet spectroscopy, Time series analysis
Polarimetry of GRB 230818A. We present a preliminary analysis of optical photometric and polarimetric observations of GRB 230818A obtained with the Liverpool Telescope starting 3.2 minutes after the alert. The optical photometry suggests a reverse shock-dominated afterglow, transitioning to forward shock at around 15 minutes. The polarization shows a low degree (upper limit 6%) early in the light curve. This is in contrast to the expected result since this regime should be dominated by the reverse shock wave that, in turn, should present a higher degree of polarization.

Keywords: Stellar jets, Gamma-ray bursts, Gamma-ray transient sources
Anthropogenic Coal Ash as a Contaminant in an Underwater Search. II. Beyond Beryllium, Lanthanum, and Uranium. It has been shown that the Beryllium, Lanthanum and Uranium concentrations in the "BeLaU" spherules are in the expected ranges of coal ash. It is reported that the average elemental concentration of 12 microspherules can be found in the COALQUAL database in 98% (49/50) of the elements examined. The "BeLaU pattern" is found to be not unique, it can be reproduced using a coal ash standard (SRM1633a) and a chondritic normalization. The ratio of rare-earth elements in the "BeLaU" spherules and the SMR1633a sample is of order unity. Comparisons against SRM1633a return only two elements with abundances statistically significantly lower than the coal ash standard of reference (or fractions of order unity), agreeing in 96% (52/54) of the elements tested. No elements show higher abundance than 10× the reference standard. Terrestrial coal ash is curiously very similar to the collected spherules. Origin from a recent meteoritic event remains uncertain.

Keywords: Micrometeorites, Meteorite composition, Chondrites
A Possible Cyclotron Feature of the Gamma-Ray Binary 4FGL J1405.1–6119. We reanalyzed the X-ray observations of the γ-ray binary candidate 4FGL J1405.1‑6119 using the XMM-Newton observations. In the X-ray spectra, we find a weak absorption feature around 2 keV in the XMM-Newton observations, which could be the cyclotron resonant scattering feature (CRSF) or so called cyclotron line of the possible neutron star (NS) in the binary. The line energy of the CRSF is ∼2 keV, implying that the magnetic field on the surface of the NS is about B ≈ 1011 G or B ≈ 1014 G depending on the cyclotron line being generated by electron or proton, respectively. This suggest that 4FGL J1405.1‑6119 hosts a weakly magnetized NS or a magnetar.

Keywords: Neutron stars, Gamma-ray astronomy, High mass x-ray binary stars, Magnetic fields
Extinction along Sightlines Sampled by the APO Catalog of DIBs. Identification of molecular carriers for diffuse interstellar bands (DIBs) may stem in part from the determination of interrelated lines using the Apache Point Observatory Catalog of DIBs. However, Pearson correlations may be impacted by the number of interstellar clouds along the sightlines. The trend of extinction with distance was constrained using Bayestar19 and Gaia DR3, and clouds were identified via step-functions and extended increasing linear progressions may be indicative of traversal through dense spiral arms. Thirteen sightlines are likely observed through more than one cloud. The hypergiants HD168625 and VI Cyg 12 are contaminated by local nebulosity and circumstellar disks. New findings presented here support the reddenings cited within the Apache Point Observatory catalog of DIBs.

Keywords: Diffuse interstellar bands
Multi-view Deep Learning for Imaging Atmospheric Cherenkov Telescopes. This research note concerns the application of deep-learning-based multi-view-imaging techniques to data from the High Energy Stereoscopic System Imaging Atmospheric Cherenkov Telescope array. We find that the earlier the fusion of layer information from different views takes place in the neural network, the better our model performs with this data. Our analysis shows that the point in the network where the information from the different views is combined is far more important for the model performance than the method used to combine the information.

Keywords: Astronomy image processing, Gamma-ray telescopes
On the Plasma Quasi-thermal Noise in the Outer Heliosphere. The recent paper by Li et al. on electron quasi-thermal noise (QTN) in the outer heliosphere is flawed. It assumes the plasma drift speed to be much smaller than the electron thermal speed, even though both quantities are of the same order of magnitude in the outer heliosphere inward of the termination shock, because of the low plasma temperature. In this case, the Langmuir wave dispersion equation and the QTN in the antenna frame are completely changed. Furthermore, these calculations neglect the shot noise, which should produce a large contribution below the plasma frequency with the Voyager antennas in the outer heliosphere.

Keywords: Space vehicle instruments, Space plasmas, Heliosphere, Plasma physics, Solar wind
The Recurrent Nova V745 Sco had a Classical Nova Eruption in 1897 July. Recurrent nova V745 Sco is discovered to have a long-lost nova eruption in 1897 July. Now with four known eruptions (in 1897, 1937, 1989, and 2014), plus two likely missed eruptions (around 1917 and 1963), the average recurrence time is 23 yr, with a fractional rms of 13%.

Keywords: Symbiotic novae, Recurrent novae, Classical novae
Intermediate Gas Phases within Turbulent Radiative Mixing Layers. Turbulent radiative mixing layers (TRMLs) occur ubiquitously in astrophysical environments; e.g., TRMLs are prevalent within galactic outflows at the intersections between hot supernovae ejecta and cold molecular clouds. A velocity shear between the rapidly outflowing hot gas and cold clouds drives the Kelvin–Helmholtz instability producing TRMLs, with radiative cooling dominating the heat transfer between the gas phases. Using hydrodynamic simulations, we have modeled TRMLs for a range of overdensities (100, 1000, 3000) applied to cold phase temperatures of 400, 103, and 104 K. The production of an intermediate gas phase at the interface between the hot and cold phases is consistently observed at ∼104 K for molecular clouds, in agreement with larger-scale wind-tunnel simulations.

Keywords: Galactic winds, Hydrodynamical simulations, Circumgalactic medium
A Spectroscopic Characterization of a Blazar Candidate Excluded by Automated Morphology Classification. Blazars are radio-loud Active Galactic Nuclei (AGNs) with their jets pointing at us at a very small angle. J064334.60–331430.29 (hereafter J0643–3314) was selected as a blazar candidate by its colors and compactness in archival radio images. In Xie et al. 2024, we introduce an algorithm to recognize likely blazars using the morphology observed in the 3 GHz Very Large Array Sky Survey. According to our algorithm, J0643–3314 is unlikely a blazar based on the two-sided jet seen in VLASS. To validate the result of our algorithm, we investigate this source further. From the extended two-sided jet lobes, the upturn radio spectrum, and the broad emission lines in the follow-up spectrum, we robustly conclude that J0643–3314 is not a blazar. We spectroscopically confirm it as a radio-loud AGN at z = 0.3, with a projected jet size of 100.4 kpc. We estimate its bolometric luminosity to be ∼6×1044 erg s‑1, black hole mass of ∼2×108 M ⊙, and Eddington ratio of ∼0.02 from Hβ and Hα broad emission lines.

Keywords: Blazars, Active galactic nuclei
High Accuracy Photodissociation Rates in VULCAN with MCRT. Photochemical processing is a key influence on the chemical compositions of exoplanet atmospheres. We develop a 1D plane-parallel Monte Carlo radiative-transfer (MCRT) path length method to calculate actinic fluxes for photochemical modeling, which we couple to the VULCAN photochemical model. Due to the flexible nature of MCRT methods, this enables accurate calculation of photodissociation rates for complex multiple scattering scenarios encountered in exoplanet atmospheres such as high altitude haze layers.

Keywords: Radiative transfer, Exoplanet atmospheres, Chemical kinetics
Enhancing Stellar Temperature Estimation through Machine Learning and Multifaceted Data Exploration. This paper employs machine learning to estimate stellar temperatures using photometric data, focusing on the GAIA ESA Archive Data Release 3 data set. The study underscores the effectiveness of neural networks in deciphering intricate relationships within the data. Notably, the addition of metallicity improves model accuracy in characterizing stellar properties. The study also investigates outlier removal techniques, specifically favoring the Isolation Forest method, showcasing its efficacy in refining model performance. Automated machine learning, facilitated by PyCaret Regressor, emerges as a valuable tool, identifying top-performing models and highlighting feature importance. The implications of this research extend beyond the specifics of stellar temperature estimation. In contemplating future directions, this study suggests the exploration of diverse data sources to ensure balanced distributions of stellar temperatures and the potential incorporation of deep learning architectures for heightened accuracy in addressing astrophysical inquiries.

Keywords: Photometric systems, Neural networks, Stellar effective temperatures, Outlier detection, Photometry
The Hybrid Debris Disk Host Star HD 21997 is a High-frequency Delta Scuti Pulsator. HD 21997 is host to a prototypical "hybrid" debris disk characterized by debris disk-like dust properties and a CO gas mass comparable to a protoplanetary disk. We use Transiting Exoplanet Survey Satellite time series photometry to demonstrate that HD 21997 is a high-frequency delta Scuti pulsator. If the mode identification can be unambiguously determined in future works, an asteroseismic age of HD 21997 may become feasible.

Keywords: Delta Scuti variable stars, Variable stars, Stellar pulsations
Satellite Visibility During the 2024 April Total Eclipse. On 2024 April 8, tens of millions of people across North America will be able to view a total solar eclipse. Such astronomical events have been important throughout history, but with nearly 10,000 satellites in orbit, we question whether total eclipses will now reveal a sky full of satellites, fundamentally changing this experience for humanity. Using the current population of Starlink satellites, we find that the brightest satellites would be naked-eye visible in dark skies, but the high sky brightness during totality will make them undetectable to the unaided eye. Our model does not take into account the effects of chance reflections from large, flat surfaces like solar panels, which we expect will cause glints and flares that could be visible from large satellites and abandoned rocket bodies. Time-lapse all-sky imaging might reveal satellites during the eclipse.

Keywords: Artificial satellites, Total eclipses
Pipeline Provenance for Analysis, Evaluation, Trust or Reproducibility. Data volumes and rates of research infrastructures will continue to increase in the upcoming years and impact how we interact with their final data products. Little of the processed data can be directly investigated and most of it will be automatically processed with as little user interaction as possible. Capturing all necessary information of such processing ensures reproducibility of the final results and generates trust in the entire process. We present Pipeline pRovenance for Analysis, Evaluation, Trust Or Reproducibility (PRAETOR), a software suite that enables automated generation, modeling, and analysis of provenance information of Python pipelines. Furthermore, the evaluation of the pipeline performance, based upon a user defined quality matrix in the provenance, enables the first step of machine learning processes, where such information can be fed into dedicated optimization procedures.

Keywords: Software documentation, Interdisciplinary astronomy, Astronomy software
Hidden Companions to Intermediate-mass Stars. XVII. Uncovering a 0.72 M <SUB>⊙</SUB>, 0.35 au Companion in the Spectroscopic Binary Sigma Sculptoris. Sigma Sculptoris is a nearby star that was suspected of being a rotating Ap variable. It was recently found not to be an Ap star but rather a 47 days single-lined spectroscopic binary. Here we report on the direct detection of the companion with a K band flux ratio of 5.5% at a projected separation of 5.16 mas based on a VLTI/GRAVITY observation. We estimate isochrone masses M  A  = 1.95M ⊙ and M  B  = 0.72M ⊙, a semimajor axis a = 0.35 au and an orbital inclination i = 27° (or 153°). The large rotational velocity of the primary (assuming spin–orbit alignment) is consistent with the lack of prominent chemical peculiarities. *Based on observations collected at the European Southern Observatory, Chile, Program ID 109.23BV.001.

Keywords: Optical interferometry, Multiple stars, A stars
Spectral Typing with Artificial Intelligence: Classifying Low-resolution Near-infrared Spectra of Standard M/L/T Dwarfs. We investigate the application of supervised machine learning models to directly infer the spectral types of ultracool dwarfs (dwarf spectral types ≥M6) using binned fluxes as feature labels. We compare the ability of two machine learning frameworks, k-Nearest Neighbor (kNN) and Random Forest (RF), to classify low-resolution near-infrared spectra of M6 to T9 dwarfs (3100 K ≳ T eff ≳ 500 K). We used a synthetic training data set of 2400 spectra generated from 24 spectral type standards and validated our models on 315 spectra with previous literature classifications. Classification accuracies within ± 1 subtype were 98.4% ± 0.7% for the kNN model and 95.6% ± 1.2% for the RF model, indicating the kNN performs marginally better for spectral-type estimation. Future studies will explore a broader range of stellar properties such as metallicity, gravity, and cloud characteristics and additional machine learning models.

Keywords: M dwarf stars, Brown dwarfs, L dwarfs, Stellar classification, Random Forests, T dwarfs
Exploring Molecular Gas toward the Magellanic Bridge. The Magellanic Bridge (MB) is a diffuse gas structure that connects the Large Magellanic Cloud with the Small Magellanic Cloud. The MB is the closest tidal interaction system between two galaxies to the Milky Way. Taking into account that young stellar objects are embedded in such gaseous structure, it is a unique laboratory to investigate gas dynamics and star formation processes in a very low metallicity environment. In this work we present a preview of the results obtained from observations made with the Atacama Pathfinder Experiment telescope toward some regions of the MB. Through the emission of the 12CO J = 2–1 line we characterize the molecular gas of these regions.

Keywords: Small Magellanic Cloud, Magellanic Stream, Large Magellanic Cloud
Photometric Analysis of the Nucleus of the Main-belt Comet 2010 LH15. We analyzed the inactive nucleus of the main-belt comet 2010 LH15 at a true anomaly of 262°. Observations using the Gemini North Telescope in 2023 July yielded an absolute R-band magnitude of (18.4 ± 0.2) mag. Assuming a C-type geometric albedo and phase function, we estimated the nucleus radius to be (0.5 ± 0.1) km. The examination of the lightcurve profile did not yield clear evidence for a rotational period shorter than 2 hr.

Keywords: Small Solar System bodies, Asteroids, Main-belt comets, Comet nuclei, Astronomy data analysis, Comets
The Host Galaxy of a Dormant, Overmassive Black Hole at z = 6.7 may be Restarting Star Formation. JWST is discovering a large population of z &gt; 4 supermassive black holes (SMBHs) that are overmassive with respect to the stellar content of their hosts. A previous study developed a physical model to interpret this overmassive population as the result of quasar feedback acting on a compact host galaxy. In this Note, we apply this model to JADES GN 1146115, a dormant SMBH at z = 6.7 whose mass is ∼40% of the host's mass in stars and accreting at ∼2% of the Eddington limit. The host has been forming stars at the low rate of ∼1 M ⊙ yr‑1 for the past ∼100 Myr. Our model suggests that this galactic system is on the verge of a resurgence of global star formation activity. This transition comes after a period of domination by the effect of its overmassive black hole, whose duration is comparable to typical quasar lifetimes.

Keywords: Supermassive black holes, Active galaxies, Star formation, Galaxy evolution, Galaxy quenching