Sazuna/UAT_keywords huggingface dataset:
New Calculations of Human-eye Colors of Cloudy Brown Dwarfs and Exoplanets. Brown dwarfs (BDs) are in fact not brown. Their name comes from their falling between red low-mass stars and dim dark giant planets in size. But what is the actual color of a BD? We can also ask this question for exoplanets: is Earth the only pale blue dot in the Universe? In this work we investigate such questions by simulating emission spectra of both cloudy and cloudless BDs and exoplanets, and converting them into colors detectable by the human eye. We find that the resulting hue depends greatly on the type of clouds in the atmosphere. Moreover, cloudy BDs turn out to be blue for the T-types and purple for the L-types. Young massive exoplanets should follow the same sequence of colors but with a delay of the L-T transition. Our results can serve both for outreach purposes and for the interpretation of observed reflectivity spectra.

Keywords: Atmospheric clouds, Brown dwarfs, Exoplanet atmospheres, Spectroscopy
The Identification of 1RXS J222335.6+074515 as a Probable Intermediate Polar. Ground-based observations, complemented by a TESS light curve, reveal the X-ray source 1RXS J222335.6+074515 likely to be an intermediate polar (IP) with a white-dwarf rotation period of 14.0923(5) minutes. A rough estimate of the X-ray luminosity places the system between the low luminosity IPs and the bulk of IPs.

Keywords: DQ Herculis stars, Cataclysmic variable stars, Binary stars, Variable stars
ColdPress: Efficient Quantile-based Compression of Photometric Redshift PDFs. ColdPress is a Python module that compresses photometric redshift probability distribution functions (PDFs) by encoding quantiles of their cumulative distribution. For a fixed packet size (the default is 80 bytes per PDF), ColdPress attains a reconstruction accuracy comparable to the sparse-basis representation method implemented in the pdf_storage module of M. Carrasco-Kind &amp; R. J. Brunner, yet reduces the computational cost by a factor of ∼7000. I describe the implementation and quantify its compression speed and reconstruction accuracy in comparison to pdf_storage for real-life PDFs from two different photometric redshift codes. ColdPress is free software, available at https://github.com/ahc-photoz/coldpress-project.

Keywords: Astronomy software
Crowded Field Photometry with Rubin: Exploring 47 Tucanae with Data Preview 1. We analyze imaging from Data Preview 1 of the Vera C. Rubin Observatory to explore the performance of early LSST pipelines in the 47 Tucanae field. The coadd-object catalog demonstrates the depth and precision possible with Rubin, recovering well-defined color–magnitude diagrams for 47 Tuc Small Magellanic Cloud. Unfortunately, the existing pipelines fail to recover sources within ∼28 pc of the cluster center, due to the extreme source density. Using Rubin's forced photometry on stars identified via Difference Imaging, we can recover sources down to ∼14 pc from the cluster center, and find 14,744 potential cluster members with this extended data set. While this forced photometry has significant systematics, our analysis showcases the potential for detailed structural studies of crowded fields with the Rubin Observatory.

Keywords: Globular star clusters, Photometry, Star clusters
The Potential Discovery of a Circumstellar Disk in M20 from Rubin First Look. We report a new potential circumstellar or protoplanetary disk along the eastern edge of the M20 H II region. The disk was discovered in the Rubin Observatory "First Look" image of the M8–M20 complex. The discovery is of note as few protoplanetary disk outside of M42 are known. No other new circumstellar disk candidates are identified in M8 or M20.

Keywords: Protoplanetary disks
Sulfur Chemistry in Early Star-forming Cores: A Non-LTE Analysis of SO<SUB>2</SUB> and SO. The chemical behavior of sulfur in the interstellar medium (ISM), particularly in the dense regions where stars form, is still far from being well understood. Questions such as which is the main sulfur reservoir in the ISM remain unanswered. Studying interstellar sulfur-bearing molecules contributes to understanding the chemical behavior of this element in the ISM. Star-forming regions in their most early phases, when complex interstellar chemistry begins to activate, are favorable sites to carry out this type of research. We present results which are complementary to recent, extensive work which made use of data from the Atacama Large Millimeter Array. We focus on the emission of SO2 and SO obtained toward 37 dense molecular cores embedded in cold clumps. Through an analysis of non–local thermodynamic equilibrium (non-LTE), the abundances of these molecular species were estimated. In general a good agreement was obtained with the LTE results previously presented.

Keywords: Molecular gas
A Minor Planet in an Outer Resonance with Uranus. We have located archival observations of the centaur 2015 OU194 from 2017 to 2018, which extend its data-arc length from 1.0 to 3.5 yr. We show that it is in an outer 3:4 mean motion resonance with Uranus, henceforth referred to as U3/4. The resonance is stable from at least 1000 kyr in the past until 500 kyr in the future. We find no mention in the literature of known objects in this resonance, or in any other resonance between the orbits of Uranus and Neptune. Looking for additional candidates, we find that 2013 RG98 also stays in U3/4 for several hundred kyr around the present epoch. A third candidate, 2014 NX65, is strongly influenced by Neptune.

Keywords: Centaur group, Asteroid dynamics, Orbital resonances
Bioburden Reductions on the Europa Clipper Spacecraft During its MEGA-trajectory Cruise to Jupiter. The Cruise-Phase Microbial Survival (CPMS) model was used to estimate the bioburden reduction on the Europa Clipper (EC) spacecraft during its transit to Jupiter based on the final flown Mars–Earth gravity assist (MEGA) trajectory, a trajectory not considered in previous work. The CPMS model evaluates the bioburden reduction due to UV radiation, temperature, and vacuum. Under the MEGA trajectory, bioburdens on external and shallow interior surfaces accumulate the highest reductions due to the synergistic effects of temperature and vacuum, contributing to hundreds of thousands of Sterility Assurance Levels (SALs). Deep internal surfaces do not reach one SAL unless heated to at least 233 K. The revised CPMS model estimates that there will be no viable bioburden remaining on or near the exterior surfaces of the EC spacecraft upon its arrival at Jupiter following the completion of the MEGA trajectory.

Keywords: Astrobiology, Europa
K<SUB>s</SUB>-band Photometry of the Extreme T Subdwarf CWISE J221706.28‑145437.6. We present deep Ks-band imaging of the extreme T subdwarf CWISE J221706.28‑145437.6. Using the new photometry, we construct its spectral energy distribution and find this object exhibits exceptionally strong collision-induced absorption in the H and K band. The comparison with the nearest benchmark extreme T subdwarf WISEA J181006.18‑101000.5 suggests the object would be cooler and more metal-poor than the benchmark. *Based on observations made with the Gran Telescopio Canarias.

Keywords: Brown dwarfs, T subdwarfs, Broad band photometry, Metallicity, T dwarfs
A Quantification Method for Plasma Exchange Across the Planetary Magnetopause Layer. A universal method is proposed to quantify plasma exchange across the planetary magnetopause layer using the mixing rate, previously validated in local kinetic simulations of Kelvin–Helmholtz (KH) boundaries. When KH waves, magnetic reconnection, and magnetosteath jets distort the magnetopause, stationary models and the streamline method struggle to define the magnetopause surface. Using three-dimensional global hybrid simulations, we trace the solar wind and planetary ions to calculate their respective mixing rates and identify their peak distributions. A distorted magnetopause is then reconstructed through triangulation, from which local fluxes are computed across each surface element. This method supports quantitative analysis of plasma entry and escape under varying solar wind conditions and is applicable to both magnetized and unmagnetized planets.

Keywords: Space weather, Solar wind, Solar-planetary interactions, Planetary science, Planetary magnetospheres
3I/ATLAS is Smaller or Rarer than It Looks. The interstellar object 3I/ATLAS shows a weak cometary activity. Its brightness suggests a maximum radius of ∼10 km (A/0.05)‑1/2 for an asteroid with an albedo A. I show that interstellar objects with that radius would amount to an interstellar mass density that is well above the expected mass budget of interstellar comets or asteroids. Given this budget, the detection rate of objects like 3I/ATLAS implies that it is a comet with a small core radius &lt;0.6 km, or a member of a rare population with a number density ≲5 × 10‑8 au‑3 for R ≳ 10 km. The second possibility would suggest that the rare population of 3I/ATLAS objects favors orbits directed towards the inner solar system rather than being randomly drawn from an isotropic velocity distribution, to accommodate their inferred detection rate.

Keywords: Exocomets, Interstellar dynamics, Interstellar objects
On the Location of the Compact Infrared Source in Cyg X-3. This note complements the article on X-ray and infrared variability of the X-ray binary Cyg X-3 (WR+c), published by me and my co-authors. In that paper, a compact infrared (IR) source was discovered in the system, located in the vicinity of the X-ray source associated with the relativistic companion. In the current note I refine the possible location of the IR source based on simple qualitative considerations.

Keywords: Neutron stars, Black holes, High mass x-ray binary stars, Stellar mass loss, Wolf-Rayet stars, Infrared photometry
Mind the Gap in the Extended Kuiper Belt: Statistically Significant Results from New Data. Our understanding of the solar system beyond the Kuiper Cliff is changing rapidly as new trans-Neptunian objects (TNOs) keep being discovered by ground-based telescopes and direct measurements from NASA's New Horizons spacecraft help in obtaining both qualitative and quantitative estimates of the physical properties of this remote region. Here, we make use of the latest data, and of the heliocentric range and range-rate of the known TNOs to identify structures beyond the Kuiper Cliff. Hartigan's dip test applied to the data gives a p-value of 0.0027 for a gap in the distribution of heliocentric ranges at ∼72 au.

Keywords: Solar system, Kuiper belt
Morphology and Stellar Populations of a Candidate Ultra-diffuse Galaxy in Early Euclid and Rubin Imaging. We present multi-wavelength imaging and analysis of a low surface brightness (LSB) dwarf galaxy in the Extended Chandra Deep Field South (ECDFS), SMDG0333094–280938, with particular emphasis on data from the Euclid space telescope and from the Vera C. Rubin Observatory. The galaxy is clumpy and blue, and appears to host globular clusters (GCs), suggesting a distance of ∼50–60 Mpc which would make the dwarf an ultra-diffuse galaxy (UDG). We carry out spectral energy distribution fitting from the far-ultraviolet to the near-infrared, in order to estimate the galaxy age and metallicity. We infer a recent peak of star formation that may have led to the formation of the UDG through feedback-driven expansion. This early analysis illustrates how Euclid and Rubin are poised to identify and characterize many thousands of UDGs and other LSB galaxies in the near future, including their GCs and stellar populations.

Keywords: Globular star clusters, Dwarf irregular galaxies, Galaxy formation, Galaxy magnitudes, Galaxy properties, Dwarf galaxies, Galaxy radii, Galaxy ages, Galaxy evolution, Galaxy masses, Galaxies, Low surface brightness galaxies
How Stable are the Impact Factors of Major Astrophysics Journals?. We examine the long-term impact factor over the past decade (2015–2024) for seven flagship journals widely used in astrophysics: ApJ, AJ, ApJL, ApJS, A&A, JCAP, and MNRAS. We checked the variation of both the traditional impact factor and the median-based impact factor, which we had studied in a previous work. We find that ApJS exhibits the largest drop in impact factor from 14.9 to 9.0, while ApJ and MNRAS show a steady decline from 6.7 to 5.2 and 5.6 to 5.0, respectively. However, the impact factors for AJ and ApJL have shown a steady increase from 4.55 to 5.35 and 6.4 to 9.7, respectively. The median-based impact factors are much more stable and show variations of at most ±1 within the last decade.

Keywords: Astronomy databases
Carbon Monoxide Emission in the Early Spectrum of the Nova V7993 Sagittarii. Spectroscopy from 0.47 to 2.5 μm is presented for the Fe II-type nova V7993 Sagittarii. The data were acquired 2025 April 6.56, eleven days after peak visible brightness. The spectrum shows strong emission from C I and Ca II, plus lines of N I, O I, and Fe II, and molecular emission from the first overtone of carbon monoxide. Modeling of the CO indicates a temperature of 4000 K and a 13C/12C abundance ratio of 0.8. A disparity between the measured reddening and the Galactic value in the direction of V7993 Sgr suggests that dust formed during prior outbursts may affect the extinction.

Keywords: Novae, Classical novae
Hidden Companions to Intermediate-mass Stars. Upgraded Multiplicity 2 → 3. XXIX. Discovery of a 1.65M<SUB>⊙</SUB>, 1.0 au Companion to Xi1 Lupi. Xi1 Lupi (ξ1 Lup) is a nearby star (A) that forms a  10.″2↔660au  intermediate-mass visual binary with ξ2 Lup (B). The fact that the primary A is both brighter and redder than the secondary B gives rise to an age contradiction for the two components. Here we report on a VLTI/GRAVITY observation that revealed that ξ1 Lup is actually a close binary: the companion has a K band flux ratio of 59.1% ± 0.2% at a projected separation ρ = 15.88 mas ↔ 1.0 au. From isochrone fitting we find masses MAa ≃ 2.0M⊙, MAb ≃ 1.65M⊙ and MB ≃ 2.0M⊙ and a system age t ≃ 450–500 Myr; the binarity of ξ1 Lup hence solves the age contradiction. The triple system might be a progenitor for a triple white dwarf system in about 1.5 Gyr depending on the de-projected separation of Aa+Ab. *Based on observations collected at the European Southern Observatory, Chile, Program ID 113.26GM.001.

Keywords: Optical interferometry, Multiple stars, A stars
MESA-QUEST: Modeling Quasi-stars in MESA. Supermassive black hole formation remains an unsolved problem. Quasi-stars have been suggested as a viable heavy-seeding mechanism. In this work, we implement methods for modeling quasi-stars previously used with the Cambridge STARS code into the 1D stellar evolution code MESA. The computational capabilities of MESA allow for more detailed simulations of quasi-star evolution due to its modularity and the ease of implementing of new physical processes and controls. Our implementation, the MESA Quasi-star Evolutionary Simulation Toolkit (MESA-QUEST), is available in a publicly accessible repository.

Keywords: Supermassive black holes, Stellar evolutionary models, Black holes
lkspacecraft: A Tool for Obtaining Orbital Properties of the Kepler and TESS Spacecraft. NASA's Kepler and TESS missions have produced image data and time-series of millions of stars, and unlocked valuable astrophysical inference. These missions both provide precise, accurate time-series. However, because of the orbital properties of the spacecraft, the data from these missions are impacted by various relativistic effects which cause position and timing aberrations. These aberrations can be calculated using the precise ephemerides of the spacecraft, which are provided by the mission via SPICE kernels. However, SPICE kernels can be difficult for users to work with, requiring a knowledge of the workings of the SPICE package, and the location and formats of the various kernels needed to build spacecraft ephemeris. lkspacecraft is a new Python package that utilizes spiceypy to provide users with a simple interface to obtain the key properties needed to correct the relativistic effects that impact Kepler, K2 and TESS data.

Keywords: Calibration, Astronomy software, Time series analysis
Updated Mutual Inclination Measurement for 14 Her b and c. The mutual inclination ψ between orbits within multi-planetary systems is difficult to measure directly. Through a joint analysis of radial velocities, Hipparcos-Gaia absolute astrometry and relative astrometry of JWST, D. C. Bardalez Gagliuffi et al. recently found two possible values of  ψbc=32‑15.1+13.6°  and  ψbc=145.0‑11.1+15.8°  for the nearby, non-transiting planet system, 14 Her. By incorporating additional astrometry from Gaia second data release (DR2), we have further constrained the orbital orientation of 14 Her b, resulting in a definitive and unambiguous mutual inclination of  ψbc=35.3‑7.3+6.8° . The unusual misaligned orbital architecture of 14 Her system may serve as a benchmark for dynamical studies.

Keywords: Exoplanet detection methods, Radial velocity, Astrometry
An Atlas of Spectroheliograms from 3641 to 6600 Å. We present a spectral atlas of solar spectroheliograms covering the wavelength range from 3641 to 6600 Å, with continuous coverage between 3711 and 5300 Å, and sparser coverage beyond this range. The spectral resolution varies between R ∼ 20,000 and 40,000, with a spectral step size between 60 and 90 mÅ, while the spatial resolution averages around  2.″5 . These observations were acquired over three months during the 2025 solar maximum, using amateur spectroheliographs (Sol'Ex and ML Astro SHG 700). The atlas is accessible via an interactive online platform with navigation tools and direct access to individual spectroheliograms.

Keywords: The Sun, Star atlases, Atomic spectroscopy
reLAISS: A Python Package for Flexible Similarity Searches of Supernovae and Their Host Galaxies. Discovery rates of supernovae are expected to surpass one million events annually with the Vera C. Rubin Observatory. With unprecedented sample sizes of both common and rare transient types, photometric classification alone will be insufficient for finding one-in-a-million events and prioritizing the 1% of events for spectroscopic follow-up observations. Here, we present reLAISS, a modified framework for similarity searches of supernovae using extracted features of Zwicky Transient Facility light curves and Pan-STARRS host galaxy photometry and built on the original LAISS framework. Unlike its predecessor, reLAISS couples interpretable light curve morphology features with extinction-corrected host-galaxy colors to probe both explosion physics and associated stellar populations simultaneously. The library allows users to customize the number of neighbors retrieved, the weight of host and light curve features, and the use of Monte Carlo simulations to ensure relevant matches when features are poorly constrained. We release reLAISS as a pip-installable package with an accompanying reference set of 20,000 features, and a set of tutorials that demonstrate the code's expanded functionality. All source code can be found at the project's GitHub repository: https://github.com/evan-reynolds/re-laiss.

Keywords: Light curves, Galaxy photometry, Open source software, Supernovae
A Possible Unidentified O III-emitting Nebula Near the Globular Cluster NGC 3201. We report the possible detection of a faint, previously undocumented O III-emitting nebular structure in the vicinity of the globular cluster NGC 3201. The structure was observed during a deep-sky imaging campaign, with a total exposure time of over 65 hr. The emission appears elongated and filamentary, with clear enhancement in the O III band. While its physical nature remains undetermined, we publish this finding to invite further investigation from the community.

Keywords: Globular star clusters, Astronomical object identification, Sky surveys, Emission nebulae, Interstellar medium, Narrow band photometry, Astronomy data visualization
The Reclassification of the Variable Star BS Uma. In this study, we present the reclassification of the star BS Uma, known as an EA-type variable star at the Variable Star Index. The SSV-UAI-GRAV research section of the Unione Astrofili Italiani (UAI) has planned an observing campaign with six ground-based observatories in 2025 May in order to study its peculiarities. From the observing sessions, combined with the available data from the All-Sky Automated Survey for Supernovae, Zwicky Transient Facility and TESS surveys, the star was reclassified as EA+BY+UV. The orbital period of the eclipses was found to be 0.349509 day, while typical modulations of BY Draconis-type variables were noted during the maximum phases. Thanks to a session of the TESS space telescope, an outburst was detected that confirmed its eruptive nature.

Keywords: Starspots, Variable stars, Eclipsing binary stars, BY Draconis stars, UV Ceti stars
Space Telescope Imaging Spectrograph Observations of Europa's Optical Aurora. We analyzed Hubble Space Telescope observations of Europa's optical aurora, yielding further insight into the composition of its tenuous atmosphere and its plasma-interaction variability. We obtained these observations of auroral emissions while Europa was in solar eclipse behind Jupiter to avoid reflected sunlight as a background signal and source of noise. We analyzed oxygen 630.0 and 636.4 nm emission line brightness profiles across the disk to constrain O2 abundances. Analyses of time-varying brightness ratios across different regions of Europa were compared with previous auroral studies in the ultraviolet and in the visible. We confirm a correlation with auroral brightness and relative distance from Jupiter's plasma sheet crossing. We find that the decorrelated set of auroral brightnesses diminishes with longer eclipse duration, suggesting a possible partial collapse of Europa's atmosphere when in eclipse.

Keywords: Hubble Space Telescope, Aurorae, Europa, Natural satellite atmospheres, Spectroscopy
Exploring Mixing Thresholds in Asteroseismic Stellar Evolution Models. Inferences from observations clearly show that mixing in stars extends beyond the convective boundaries defined by mixing length theory. This triggered the proposal of a variety of prescriptions to include additional mixing in stellar models. These prescriptions typically introduce free parameters to set the extent of the additional mixing and may also introduce numerical parameters. In the case of exponential overshooting, one must decide the threshold at which the exponential decay of the mixing coefficient can be treated as zero. Using the MESA stellar evolution code, I explore the effect of varying this parameter on asteroseismic models of main-sequence stars with growing convective cores. From this, I conclude that overshoot_D_min should be set to 10‑2 cm2 s‑1 or lower for these stars. The default value in MESA is four orders of magnitude higher than this recommendation, which results in discontinuous evolution.

Keywords: Asteroseismology, Stellar evolutionary models
Palomar and Apache Point Spectrophotometry of Interstellar Comet 3I/ATLAS. On 2025 July 1st the third interstellar object, 3I/ATLAS or C/2025 N1 (ATLAS), was discovered, with an eccentricity of e = 6.15 ± 0.01 and perihelion of q = 1.357 ± 0.001 au. We report our initial visible to near-infrared (420–1000 nm) spectrophotometry of 3I/ATLAS using both the Palomar 200 inch telescope and Apache Point Observatory. We measure 3I/ATLAS to have a red spectral slope of 19%/100 nm in the 420–700 nm range, and a more neutral 6%/100 nm slope over 700–1000 nm. We detect no notable emission features such as from C2.

Keywords: Interstellar objects, Spectroscopy