Sazuna/UAT_keywords huggingface dataset:
Deep Imaging of the Very Isolated Dwarf Galaxy NGC 6789. We present deep optical imaging of the extremely isolated dwarf galaxy NGC 6789, obtained with the new 2 m Two-meter Twin Telescope at Teide Observatory. Despite its location in the Local Void, NGC 6789 exhibits surprising recent central star formation equivalent to approximately 4% of its total stellar mass. The origin of the gas necessary for this level of star formation remains unknown. Our data reach surface brightness limits of 29.8, 29.4, and 28.9 mag arcsec−2 in the Sloan g, r, and i filters, respectively, and reveal no evidence of tidal features or merger remnants down to ∼30 mag arcsec−2 (or equivalently, at a radial distance larger than 1.6 kpc). The galaxy's undisturbed outer elliptical morphology suggests that its recent central star formation was likely produced by either in-situ residual gas or by the accretion of external pristine gas not associated with a minor merging activity.

Keywords: Dwarf galaxies
An Independent Assessment of the International Sunspot Number since 1996. The International Sunspot Number (Ri) provides a long-term measure of solar activity. This study compares Ri with sunspot numbers independently derived from Solar and Heliospheric Observatory/Michelson Doppler Imager and Solar Dynamics Observatory/Helioseismic and Magnetic Imager continuum imagery, United States Air Force/National Oceanic and Atmospheric Administration Solar Region Summary reports, and the author's own white-light observations from 1996 to 2025. Scaling factors (k) were determined for each dataset, and monthly values were compared over Solar Cycles 23─25. The results show excellent agreement between Ri and all the independent datasets, with no evidence of the discrepancy reported by L. Svalgaard during 2014─2015. These findings support the consistency of Ri and highlight the reliability of satellite-based sunspot number derivation.

Keywords: Solar cycle, Sunspot cycle, Sunspots, Sunspot number
Enhancing Multiplet Alignment Measurements with Imaging. We demonstrate that measurements of the gravitational tidal field made with spectroscopic redshifts can be improved with information from imaging surveys. The average orientation of small groups of galaxies, or "multiplets" is correlated with large-scale structure and is used to measure the direction of tidal forces. Previously, multiplet intrinsic alignment has been measured in DESI using galaxies that have spectroscopic redshifts. The DESI Legacy Imaging catalog can be used to supplement multiplet catalogs. Our findings show that galaxy positions from the imaging catalog produce a measurement similar to the measurements made with only spectroscopic data. This demonstrates that imaging can improve our signal-to-noise ratio for multiplet alignment in DESI.

Keywords: Cosmology, Observational cosmology, Cosmic web, Large-scale structure of the universe
Survival of Higher Overdensity Cold Gas in a Turbulent, Multiphase Medium. Cold gas clouds embedded in a hot, turbulent medium are typically short-lived due to disruptive hydrodynamic instabilities. However, radiative cooling might allow such clouds to survive and grow. We present 3D Athena++ simulations of clouds with a density contrast of χ = 1000, exploring turbulent Mach numbers  M∈(0.25,0.75)  and cloud radii chosen to span cooling-to-crushing ratios α ∈ [0.001, 10]. We find a shift in the survival boundary, with cloud survival occurring only when the cooling-to-cloud-crushing ratio (tcool,mix/tcc) ≲ 0.01, which is lower than the expected boundary of ∼1. This result shows that it is more difficult for higher over-density cold clouds to survive in a turbulent, hot medium, and suggests another "survival criterion."

Keywords: Galaxy clusters, Hydrodynamical simulations, Intracluster medium
A Revised Three-dimensional Visualization of the Local Group of Galaxies. A new three-dimensional reconstruction of the Local Group (142 confirmed members) and nearest galaxies (6 members) is presented, addressing the lack of up-to-date visual representations that reflect the rapid pace of discoveries in the field. While numerous studies have refined distance measurements and catalogued newly discovered dwarf galaxies, most existing educational-graphic visualizations remain not updated or fragmented. This project offers a comprehensive view based on published data and the constantly updated Local Volume Galaxies database, using a Cartesian visualization to depict accurate spatial relationships among the galaxies of the Local Group. The resulting map not only updates previous visualizations by incorporating new members and refined distances, but also highlights the growing challenge of maintaining a consistent nomenclature and reference system for the Local Group. It is both visually attractive, and serves as a scientific and educational tool aimed at reflecting the evolving structure of our galactic neighbourhood.

Keywords: Local Group, Galaxy clusters, Spiral galaxies, Irregular galaxies, Dwarf galaxies, Galaxy groups, Dwarf spheroidal galaxies, Elliptical galaxies, Magellanic irregular galaxies, Andromeda Galaxy, Milky Way Galaxy
The Nature of the Bright A3 V Star HD 145570 (ψ Scorpii, HR 6031). Abundances are measured for 19 chemical elements for the bright A3 V star, HD 145570, by modeling a coadded FEROS spectrum. The following excesses/deficiencies are found: carbon (−0.26 dex), oxygen (−0.30), sodium (+0.40), magnesium (−0.02), aluminum (0.00 upper limit), silicon (−0.22), sulfur (+0.18), calcium (−0.12), scandium (−0.05), titanium (−0.12), vanadium (0.00), chromium (−0.07), manganese (−0.52), iron (−0.21), nickel (−0.35), strontium (0.00), yttrium (0.30), zirconium (+0.18), barium (+0.18). The underabundance in calcium and overabundances of yttrium, zirconium and barium favor an Am status. However the presence of Rare Earths could not be established without ambiguity because of the broadening of the lines by rotation.

Keywords: Am stars, A stars
Reproducing High-energy Neutrino Emission from Short Gamma-Ray Bursts: Validation and Application to GRB 170817A. I reproduce the analytical framework of S. S. Kimura et al. for high-energy neutrino emission from short gamma-ray bursts. After verifying the model against S. S. Kimura et al., I apply it to GRB 170817A, emphasizing that the burst is established to be viewed off-axis and using luminosity and energy derived independently in my thesis from Fermi-GBM spectral analysis. For the observed off-axis case, the predicted neutrino fluence yields Nμ ≪ 1 at 40 Mpc, consistent with IceCube's nondetection. A controlled on-axis test with otherwise similar microphysics produces a dramatically higher fluence and essentially certain detectability at 40 Mpc. This comparison demonstrates how geometric effects will shape future detections with IceCube-Gen2. *Detailed code for this work is available at https://doi.org/10.5281/zenodo.17569170 and https://github.com/svamshi-9384/sgrb_neutrino_replication/.

Keywords: Neutrino astronomy, Gamma-ray bursts
A Mid-latitude Non-detection of a Magnetic Crochet during the 2025 November 4 X1.8 Solar Flare. I investigated the near-Earth response to the 2025 November 4 X1.8 solar flare (peak 17:34 UT) using seven days of GOES-18 soft X-ray, integral proton, and magnetometer data, together with one-minute scalar geomagnetic measurements from USGS/INTERMAGNET observatories and a campus Geometrics G-857. The GOES 0.1─0.8 nm channel shows a clean rise to 1.8 × 10−4 W m−2 and decay by ≍17:51 UT, with no major SEP onset or sudden-commencement-like step in the magnetometer record. I searched for a magnetic crochet by constructing detrended total-field variations ∆F over a flare-centered window and applying timing, morphology, coherence, and amplitude criteria. No station exhibits a clear, flare-synchronous signature. At mid-latitudes, including the campus site, I place a conservative upper limit of ≲5 nT. This well-constrained non-detection complements recent high-latitude and cusp detections, indicating that radiatively strong but magnetospherically quiet X-class flares may not produce observable crochets at mid-latitudes.

Keywords: Geomagnetic fields, Solar flares, Space weather, Planetary science, Planetary magnetospheres
No Pulsar Detected in Reprocessed Archival Parkes Observations of SNR 1987A. We have reprocessed the available archival radio pulsar search observations of SNR 1987A taken with the Parkes 64 m telescope, some of which have not been previously published. We conducted a standard periodicity search on these data as well as a single pulse search at a range of dispersion measures. We found no convincing candidate signals, and we calculate flux density, luminosity, and single pulse fluence limits from these observations. The derived luminosity limits are comparable to the luminosities of three young, energetic pulsars (the Crab pulsar, PSR B0540−69, and PSR J0537−6910), and so we cannot rule out the existence of a pulsar in SNR 1987A with a similar radio luminosity.

Keywords: Supernova remnants, Large Magellanic Cloud, Pulsars
Rapid Dynamical Evolution in the Arjuna Asteroid Belt: Apollo 2022 RD<SUB>2</SUB> Goes from Mini-moon to Virtual Impactor in About 40 yr. The Arjunas populate a secondary asteroid belt that occupies the region where the Earth─Moon system orbits the Sun. Some Arjunas are trapped in the 1:1 mean-motion resonance with Earth as horseshoe librators, experiencing slow close encounters with the Earth─Moon system that may lead to temporary gravitational captures or mini-moon events, and sudden changes in their orbital elements. Here, we show that the small asteroid 2022 RD2 has a Lyapunov time under 20 yr, it could be trapped in the 1:1 mean-motion resonance with Earth as a horseshoe librator, and it will become a mini-moon for a few months in 2043─2044, to turn into a virtual impactor that might hit Earth starting in 2080.

Keywords: Solar system, Asteroids, Asteroid dynamics
Detectability of Dust and Ion Tails of Interstellar Comet 3I/ATLAS by Europa Clipper. The Europa Clipper spacecraft is located about 1 au downstream from the interstellar comet 3I/ATLAS around its perihelion. Here we model the propagation of pickup ions and cometary dust originating from 3I/ATLAS to examine their detectability by the Europa Clipper spacecraft. Our results suggest that while pick up detection is possible, the dust tail will not reach the Clipper spacecraft, Mars, nor the Jovian system.

Keywords: Comet tails, Comet ion tails, Comet dust tails, Interstellar objects
Hidden Companions to Intermediate-mass Stars. Upgraded Multiplicity 3 → 4. XXXII. Discovery of a 1.17M<SUB>⊙</SUB>, 0.44 au Companion to e Geminorum A. e Geminorum is a nearby  ρ=7.″4↔220au  visual binary (A+B) that also has a wide ρ = 152″ ↔ 4560 au companion. Here we show that e Gem is actually a quadruple system based on a VLTI/GRAVITY observation: the visual primary is itself a close binary with a K band flux ratio of 31% at a projected separation ρ = 13.46 mas ↔ 0.44 au. Isochrone fitting implies masses MAa ≃ 1.61M⊙ and MAb ≃ 1.17M⊙. Ab can explain the X-ray emission of e Gem A. Nontrivial evolution is expected when Aa fills its Roche lobe as it ascends the red-giant branch in about 5 Gyr. *Based on observations collected at the European Southern Observatory, Chile, Program ID 114.27DS.001.

Keywords: Optical interferometry, Multiple stars, F stars, A stars
Investigation of the Structural Properties of Brightest Cluster Galaxies. Brightest Cluster Galaxies (BCGs) are the largest galaxies in clusters, residing at their centers, tracing hierarchical structure formation. This study analyzes the structural properties of BCGs from the Abell cluster catalog (0.03 &lt; z &lt; 0.08) using archival Flexible Image Transport System imaging data from the Kitt Peak National Observatory 4 m telescope. AstroPhot-based Sérsic profile fitting extracts the key structural parameters, and incorporating point spread function convolution into the models produces improved residuals. Residual image analysis reveals consistent asymmetries, filaments, and tidal features, supporting hierarchical growth through mergers and accretion, and intracluster light highlights cluster dynamics' influence on BCG morphology. Higher Sérsic indices (n ∼ 4−8) indicate concentrated cores and extended halos, supporting mass growth via accretion and dry mergers. The Kormendy relation with a derived slope ( a  = 3.40), verifies that BCGs follow scaling laws. The results support the two-phase formation model: early compaction (z &gt; 2) forms dense cores, followed by merger-driven growth (z &lt; 2).

Keywords: Brightest cluster galaxies, Galaxy formation, Galaxy evolution
A New FU Orionis Accretion Outburst in the W5 H II Region. We announce a recently detected outburst that is currently only a few months old, and probably of FU Orionis type. The progenitor to the outburst was an emission-line, flat-spectrum spectral energy distribution young stellar object located in the W5 region, though somewhat outside the main star formation action. We present optical, near-infrared, and mid-infrared lightcurves that illustrate the quiescent state of [KAG2008] 13656 and its subsequent ∆r ≍ −4 mag and ∆J ≍ −3 mag outburst over ∼75 days in late-2025. Follow-up optical and near-infrared spectroscopy confirms the expected features from an FU Ori disk and outflow.

Keywords: Young stellar objects, FU Orionis stars
Study of the Variability of CzeV961, Two Reclassifications, and a Discovery. In this article, we present the study for the reclassification of the variability of the star CzeV961 by SSV-UAI-GRAV, classified by Variable Star Index as an EW eclipsing binary. In the same field of observation, there were two variable stars already discovered by Gaia but of an undefined type. In examining the comparison stars for our study, we then discovered a new variable star that had not yet been classified. The star CzeV961 turned out to be a Gamma Doradus variable star, like the two Gaia stars, while the newly discovered variable turned out to be an RS Canum Venaticorum type star.

Keywords: Starspots, Binary stars, Variable stars, RS Canum Venaticorum variable stars, Gamma Doradus variable stars, Multi-periodic variable stars
A Pipeline for Generating Realistic Artificial Ultra-faint Dwarf Galaxies. Ultra-Faint Dwarf Galaxies (UFDs) are among the lowest-mass and least-luminous galaxies known. Using algorithmic and visual inspection, they are first identified as galaxy candidates in ground-based imaging. UFDs at distances greater than ∼300 kpc are subsequently verified through space-based observations. However, the oversubscription of space-based telescopes, coupled with the difficulty of resolving faint systems at these distances, restricts the number of confirmed UFDs. Hence, the training data available to validate and refine existing search algorithms remains limited. We present a pipeline that combines existing tools to generate artificial UFDs that closely resemble known UFDs in ground-based images. We further extract photometric information with realistic observational uncertainties. This pipeline significantly increases the available training data with tens of thousands of artificial candidates, enabling advancement of UFD search algorithms and the discovery of UFDs beyond the current observational limits.

Keywords: Astronomy software, Gaussian mixture model, Dwarf galaxies, Astronomy image processing
Long-period Transit Searches Should Use a Wider Range of Durations. We present a method for computing upper and lower limits to the expected duration of planetary transits given a range for the parameters of the host star, while explicitly accounting for non-zero impact parameter and eccentricity, and placing a basic constraint on the orbital stability through a minimum planet─star separation at periastron. We find that, especially at longer periods, the transit can be considerably shorter or longer than previous searches have assumed. No transits are known with such short or long transit durations, but it is unclear whether this is a real feature of the planet population or a combination of transit probability, observational bias, and detection bias.

Keywords: Exoplanet detection methods, Transits, Exoplanets
The Need for Multiangle BRDF Laboratory Measurements to Model Rocky Exoplanet Surface Reflectance and Emission. Synthetic spectra of airless rocky exoplanets rely on laboratory measurements of planetary analogue materials to determine their optical and photometric properties. Realistic surface modeling requires several wavelength-dependent parameters, including the single-scattering albedo, phase-function asymmetry factor, and the amplitude and width of the opposition surge. However, existing laboratory datasets generally provide reflectance only at a fixed incidence-emission geometry, leaving these key photometric quantities highly degenerate or unconstrained. As a result, current surface models resort to simplified scalings to approximate reflectance and emissivity. With this Note, I draw attention to the urgent need for multi-angular, multi-spectral bidirectional reflectance distribution function measurements of planetary-analogue materials. Such datasets will be essential for interpreting reflected and emitted spectra of rocky exoplanets with upcoming facilities such as HWO, LIFE, and future direct-imaging missions.

Keywords: Solar system terrestrial planets
The Calm before the Storm: High Spatial Resolution Mosaic of Active Region NOAA 14274 at the Onset of an X1.2 Flare. Active region NOAA 14274 produced some of the strongest flares of Solar Cycle 25, including the X1.2 and X5.1 flares on 2025 November 10 and 11, respectively. We present the first large mosaic of speckle-restored images obtained with the improved High-resolution Fast Imager at the 1.5 m GREGOR solar telescope at the Observatorio del Teide in Izaña, Tenerife, Spain. The observations were obtained approximately 30 minutes before the onset of the X1.2 flare. The active region exhibited strongly curved penumbral filaments, sunspot rotation, and shear motions along the polarity inversion line, which led to a highly stressed magnetic field configuration that stored sufficient energy to release multiple M- and X-class flares. The first flare signatures appeared as small-scale brightenings, each with a width of a few tenths of an arcsecond, that trace penumbral filaments in the trailing sunspot.

Keywords: Solar flares, Solar photosphere, Solar physics, Speckle interferometry, Solar chromosphere, High angular resolution
SED Fitting for Algol Binaries with Some Observations Taken during the Eclipses. I present a study of two Algol type systems, which have anomalous Spectral Energy Distribution fitting. It appears that these anomaly is simply caused by several observations taken during the eclipse, when only the cool component of the binary was visible. I take this into account and provide good fits using all available observations.

Keywords: Algol variable stars, Spectral energy distribution
Stochastic Pathways to Early Supermassive Black Hole Growth. The rapid appearance of ∼109 M⊙ black holes by z &gt; 7 remains a major challenge for models of early black hole assembly. Standard Eddington-limited growth produces slow exponential mass increase, requiring either massive initial seeds or extended super-Eddington phases. Here I explore a minimal stochastic alternative: geometric Brownian motion with multiplicative Poisson jumps representing intermittent accretion bursts. I adopt the Itô stochastic differential equation formulation, ensuring consistency between analytic expectations and the Euler─Maruyama numerical integration. Even modest burst amplitudes (F = 1.5─3.0) significantly accelerate median growth relative to the deterministic Eddington track, and naturally produce log-normal mass distributions reminiscent of hydrodynamic simulations variability. This short communication provides an illustrative link between deterministic accretion theory and feedback-regulated, bursty accretion models.

Keywords: High-redshift galaxies, Galaxies
Tracking the Activity of the Interstellar Object 3I/ATLAS through Its Perihelion. In order to facilitate interplanetary spacecraft observations of 3I/ATLAS, we have monitored and predicted the optical properties of its coma using both ground and space-based observations. Here, we describe how the data from space-based solar coronagraphs and the Polarimeter to Unify the Corona and Heliosphere mission enabled tracking of 3I/ATLAS's optical magnitude throughout its entire perihelion passage, including the period between 2025 October 8 and 30, when it was not visible from Earth.

Keywords: Exocomets, Comet dynamics, Interstellar objects
Gravity-darkening Exponents for MESA Stellar Evolution Models. In this Research Note we present new gravity-darkening exponents (β) for several stellar evolution models from the zero-age main sequence up to the giant phase. The models were computed using the Modules for Experiments in Stellar Astrophysics code (version 7385) for the composition X = 0.70 and Z = 0.02, adopting A09 opacities and a mixing length parameter of αMLT = 1.84. Results were calculated using the triangle strategy, for initial stellar masses of 1.0, 1.5, 2.0, 2.5, 3.0, 5.0, 7.0, 10.0, 15.0, and 20.0 M⊙, and provide an update on previously available β values that used older models.

Keywords: Stellar evolutionary models, Exoplanet astronomy, Tides, Eclipsing binary stars, Gravity darkening
Non-detection of J1407 b in ALMA Band 7 Observations. We report on Atacama Large Millimeter/submillimeter Array (ALMA) Band 7 continuum observations toward the star 1SWASP J140747.93-394542.6 taken in mid 2024. These observations were a follow-up of a previous detection of an emission source in the J1407 field of view at an unexpected position in 2017. Proper motion analysis indicated that if this were the object responsible for the 2007 eclipse of J1407, it would be detectable at a new position, but still within an ALMA field of view in 2024. Here we present the non-detection of emission in the ALMA field of view (to a 1σ upper limit of 17.5 μJy), at both the 2017 position, and the position expected from proper motions. We place upper limits on a source at the proper motion corrected expected location in this 2024 data, and rule out the possibility of a dusty object being responsible for the 2007 eclipse.

Keywords: Eclipses, Exoplanet rings, Interstellar medium, Circumstellar disks, Submillimeter astronomy
Confirming the Magnetic Field Detection at the Surface of χ Cyg. We present spectropolarimetric observations of χ Cygni obtained with Neo-Narval at Télescope Bernard Lyot in 2025. We obtained observations across three epochs (2025 July, August, and October) near maximum light to search for magnetic field signatures at the stellar photosphere. We detected a clear circular polarization signal in the 2025 August observations (pulsation phases 0.99─0.01). We measure a mean longitudinal magnetic field of Bl = 3.4 ± 0.6 G. No detections were obtained for the 2025 July and October epochs. The pulsation-phase dependence suggests that field detection is tied to specific shock conditions near maximum light.

Keywords: Stellar atmospheres
Generating LSB-optimized Synthetic Images for Simulated Galaxies. We introduce an emission-biasing scheme in the SKIRT radiative transfer code that enables efficient generation of synthetic galaxy images optimized for low-surface-brightness (LSB) science. Standard Monte Carlo radiative transfer simulations achieve high signal-to-noise in bright regions but require prohibitively many photon packets to reach reliable depth in galaxy outskirts. By assigning stellar particles bias factors that scale with their smoothing lengths, our method boosts photon emission from low-density regions while conserving energy through weight corrections. Tests on a Milky Way-like galaxy from the TNG50 cosmological simulation show that bias factors proportional to the smoothing length substantially extend the reliable LSB regime, providing an inexpensive improvement for deep synthetic imaging of simulated galaxies.

Keywords: Radiative transfer simulations, Galaxy evolution