Sazuna/UAT_keywords huggingface dataset:
Science with a Large Field-of-view Polarization Survey: The Large Array Survey Telescope Polarization Node (LAST-P). Optical polarimetry provides information on the geometry of the emitting region, the magnetic field configuration and the properties of dust in astrophysical sources. Current state-of-the-art instruments typically have a small field of view (FoV), which poses a challenge for conducting wide surveys. We propose the construction of the Large Array Survey Telescope Polarization Node (LAST-P), a wide-field array of optical polarimeters. LAST-P is designed for high-cadence (≲1 day) polarization monitoring of numerous astrophysical transients, such as the early phases of gamma-ray bursts, supernovae, and novae. Furthermore, LAST-P will facilitate the creation of extensive polarization catalogs for X-ray binaries and white dwarfs, alongside a large FoV study of the interstellar medium. In survey mode, LAST-P will cover a FoV of 88.8 deg2. With a 15 ×1 minutes exposure, the instrument will be capable of measuring polarization of sources as faint as Gaia Bp-magnitude ∼20.9. The precision on the linear polarization degree will reach 0.7%, 1.5%, and 3.5% for sources with magnitudes 17, 18, and 19, respectively, for a seeing of 2 .″ 7, air mass of about 1 for observations in dark locations. We propose three distinct non-simultaneous survey strategies, among them an active galactic nuclei (AGN) strategy for long-term monitoring of ∼200 AGN with &lt;1 day cadence. In this paper, we present the predicted sensitivity of the instrument and outline the various science cases it is designed to explore.

Keywords: Gamma-ray bursts, Polarimeters, Relativistic jets, White dwarf stars, Astronomical instrumentation, Active galactic nuclei, Photometry, Extragalactic astronomy, Optical observatories, Polarimetry
The Solirad (So) as a Convenient Unit for Quoting Astronomical Irradiances for Planetary Insolations and Exoplanetary Instellations. Measurements of physical parameters for stars and (exo)planets are often quoted in units normalized to the Sun and/or Earth. The nominal total solar irradiance,  S⊙N , while based on a current best estimate with uncertainties, was adopted to be an exact reference value of 1361 W m−2 by IAU 2015 Resolution B3, corresponding to "the mean total electromagnetic energy from the Sun, integrated over all wavelengths, incident per unit area per unit time at distance 1 au." In the planetary and exoplanetary science literature, the units employed for "flux," "insolation," "instellation," etc., are often cumbersome or inconsistent. To simplify the quoting of irradiance units for astronomical applications, we introduce the portmanteau solirad, short for solar irradiance, as an abbreviated version of the longer IAU term "nominal total solar irradiance." The solirad (So) is a unit of irradiance, where 1 solirad = 1 So = 1361 W m−2, equivalent to the IAU nominal total solar irradiance, and to an apparent bolometric magnitude of mbol ≃ −26.832 mag (per IAU 2015 Resolution B2).

Keywords: Exoplanets, Solar system planets, Fundamental parameters of stars, The Sun, Solar spectral irradiance, Solar constant
Machine Learning-Driven Analysis of kSZ Maps to Predict CMB Optical Depth τ. Upcoming measurements of the kinetic Sunyaev─Zel'dovich (kSZ) effect, which results from Cosmic Microwave Background (CMB) photons scattering off moving electrons, offer a powerful probe of the Epoch of Reionization (EoR). The kSZ signal contains key information about the timing, duration, and spatial structure of the EoR. A precise measurement of the CMB optical depth τ, a key parameter that characterizes the universe's integrated electron density, would significantly constrain models of early structure formation. However, the weak kSZ signal is difficult to extract from CMB observations due to significant contamination from astrophysical foregrounds. We present a machine learning approach to extract τ from simulated kSZ maps. We train advanced machine learning models, including swin transformers, on high-resolution seminumeric simulations of the kSZ signal. To robustly quantify prediction uncertainties of τ, we employ the Laplace Approximation (LA). This approach provides an efficient and principled Gaussian approximation to the posterior distribution over the model's weights, allowing for reliable error estimation. We investigate and compare two distinct application modes: a post-hoc LA applied to a pre-trained model, and an online LA where model weights and hyperparameters are optimized jointly by maximizing the marginal likelihood. This proof-of-concept approach provides a framework for constraining τ and its associated uncertainty, which could be adapted for analysis of upcoming CMB surveys like the Simons Observatory and CMB-S4.

Keywords: Bayesian statistics, Neural networks, Cosmic microwave background radiation, Sunyaev-Zeldovich effect, Reionization
Unveiling Hidden Clustering: An Unsupervised Machine Learning Study of Repeating FRB 20220912A. Fast Radio Bursts (FRBs) are millisecond-duration radio transients of extragalactic origin. Classifying repeating FRBs is essential for understanding their emission mechanisms, but remains challenging due to their short durations, high variability, and increasing data volume. Traditional methods often rely on subjective criteria and struggle with high-dimensional data. In this study, we apply an unsupervised machine learning framework—combining Uniform Manifold Approximation and Projection and Hierarchical Density-Based Spatial Clustering of Applications with Noise—to eight observed parameters from FRB 20220912A. Our analysis reveals three distinct clusters of bursts with varying spectral and fluence properties. Comparisons with clustering studies on other repeaters, show that some of our clusters share similar features, such as FRB 20201124A and FRB 121102, suggesting possible common emission mechanisms. We also provide qualitative interpretations for each cluster, highlighting the spectral diversity within a single source. Notably, one cluster shows broadband emission and high fluence, typically seen in non-repeating FRBs, raising the possibility that some non-repeaters may be misclassified repeaters due to observational limitations. Our results demonstrate the utility of machine learning in uncovering intrinsic diversity in FRB emission and provide a foundation for future classification studies.

Keywords: Radio bursts, Time domain astronomy, Radio transient sources
Active Galactic Nuclei Do Not Exhibit Strictly Sinusoidal Brightness Variations. Periodic variability in active galactic nuclei (AGNs) light curves has been proposed as a signature of close supermassive black hole (SMBH) binaries. Recently, 181 candidate SMBH binaries were identified in Gaia DR3 based on apparently stable sinusoidal variability in their ∼1000 days light curves. By supplementing Gaia photometry with longer-baseline light curves from the Zwicky Transient Facility (ZTF) and the Catalina Real Time Transient Survey, we test whether the reported periodic signals persist beyond the Gaia DR3 time window. We find that in all 116 cases with available ZTF data, the Gaia-inferred periodic model fails to predict subsequent variability, which appears stochastic rather than periodic. The periodic candidates thus overwhelmingly appear to be false positives; red noise contamination appears to be the primary source of false detections. We conclude that truly periodic and sinusoidal AGN variability is exceedingly rare, with at most a few in 106 AGN exhibiting it on 100─1000 days timescales. Models predict that the Gaia AGN light curve sample should contain dozens of true SMBH binaries with periods within the observational baseline, so the lack of strictly periodic light curves in the sample suggests that most short-period binary AGN do not have light curves dominated by simple sinusoidal periodicity.

Keywords: Supermassive black holes, Light curves, Quasars
Chemical Signatures of AGB Mass Transfer in Gaia White Dwarf Companions. We present a homogeneous abundance analysis of 160 main-sequence stars in astrometric white-dwarf + main-sequence (WD+MS) binaries with orbits from Gaia DR3. These systems have Astronomical unit-scale separations and are thought to have undergone mass transfer (MT) when the WD progenitor was an asymptotic giant branch (AGB) star. Using high-resolution spectroscopy, we measure chemical abundances of the MS stars, focusing on s-process elements. Since s-process nucleosynthesis occurs mainly in AGB stars, s-process enhancement in the MS star is a key signature of accretion from an AGB companion. We identify 43 barium dwarfs—39 of them newly discovered—roughly doubling the known population in astrometric WD+MS binaries and extending it to lower metallicities than previously studied. The s-process abundances show large star-to-star variations that correlate with component masses and with metallicity but not with orbital separation. At the lowest metallicities, three barium dwarfs display strong CH and C2 absorption bands, confirming a link between barium stars and carbon enhanced metal-poor-s stars and implying that AGB mass transfer usually leads to strong carbon enhancement at low metallicity. By comparing the observed abundance patterns to AGB nucleosynthesis models, we show that the diversity of s-process enhancements can be explained by variations in donor mass, metallicity, and most importantly, the number of thermal pulses the AGB star experienced before the onset of MT. Variation in the depth of the accretors' convective envelopes, with which accreted material is diluted, strengthens correlations with MS star mass and metallicity. Our results establish Gaia WD+MS binaries—which are homogeneously selected and probe shorter orbital periods than previous barium-star samples—as a powerful laboratory for constraining mass transfer physics and the origin of chemically peculiar stars.

Keywords: Binary stars, White dwarf stars, Chemical abundances, Asymptotic giant branch stars, Spectroscopy
Intermediate-mass Stripped Stars in the Magellanic Clouds: Forward Modeling the Observed Population Discovered Via UV Excess. Stripped stars are hot, helium-rich stars formed when binary interactions remove a star's hydrogen envelope. While low-mass (≲1 M⊙) and high-mass (≳8 M⊙) stripped stars are well studied as hot subdwarfs and Wolf─Rayet stars, their intermediate-mass counterparts (1─8 M⊙) have only recently been discovered. The Stripped-Star Ultraviolet Magellanic Cloud Survey (SUMS) identified UV-excess sources (i.e., sources lying blueward of the main sequence) in the Magellanic Clouds using Swift-UVOT photometry and selected 820 photometric stripped-star candidates. However, the completeness and purity of this sample remain poorly understood. We forward model the population of stripped stars in the Magellanic Clouds using a binary population synthesis model combined with spatially resolved star formation histories and simulated UV photometry. To assess survey sensitivity, we inject simulated sources into real Swift-UVOT images and reproduce the SUMS selection process, including crowding, extinction, and photometric quality cuts. For the SMC and LMC, we respectively recover 31% and 15% of sources with intrinsic UV excess, and 11% and 7% of all stripped stars. The rest are missed due to dilution by luminous companions, crowding, high extinction, and limited survey coverage. The observed population is biased toward systems with low-mass companions formed by common envelope evolution and systems with compact object companions. We predict contamination of the observed stripped-star candidates by main-sequence stars with spurious UV excess due to crowding and provide guidelines for selecting higher-purity subsamples. Our population synthesis model matches the number and properties of observed stripped star candidates with masses of (2─5) M⊙ well. It underpredicts the number of lower- and higher-mass candidates, perhaps due to contamination.

Keywords: Magellanic Clouds, Binary stars, Interacting binary stars, Ultraviolet surveys
Hidden in Plain Sight II: Characterizing the Luminous Companion to κ Velorum with VLTI/GRAVITY. κ Vel (Markeb, HD 81188, 天社五) is one of the brightest stars in the Southern sky and has long been known to be a single-lined spectroscopic binary. The binary mass function is large, f(M) = 1.15 M⊙, suggesting that the bright (V = 2.5) B2IV star may host a dark, compact object companion. We use VLTI/GRAVITY observations to definitively test this possibility by directly resolving the binary. We detect a main sequence B star companion and rule out the compact object scenario. By combining the relative astrometric orbit and archival radial velocities, we report an updated precise characterization of the orbit (period P = 116.795 ± 0.002 days, eccentricity e = 0.1764 ± 0.0004, inclination i = 74 .° 04 ± 0 .° 01) and estimate the masses of the B stars. Using the original Hipparcos parallax measurement ϖ = 6.05 ± 0.48 mas, we find  M1=10−2+4M⊙  and M2 = 6.9 ± 1.0 M⊙. The uncertainties on the masses are primarily driven by the uncertain parallax, which we find is likely biased by the orbital motion. We use an archival UVES spectrum and MIST evolutionary tracks to refine our mass estimates. Finally, we discuss how interferometry and high-contrast imaging may be used to characterize other candidate star+compact object binaries, including those that will be discovered with Gaia DR4, as part of a larger effort to uncover the hidden population of black holes in the Milky Way.

Keywords: Binary stars, Compact objects, Interferometry
Low-luminosity Type IIP Supernovae from the Zwicky Transient Facility Census of the Local Universe. II. Lightcurve Analysis. The Zwicky Transient Facility Census of the Local Universe survey yielded a sample of 330 Type IIP supernovae (SNe) with well-constrained peak luminosities. In paper I, we measured their luminosity function and volumetric rate. Here (paper II), we present the largest systematic study of lightcurve properties for Type IIP SNe from a volume-limited survey, analyzing a selected subset of 129 events, including 16 low-luminosity Type IIP (LLIIP) SNe with Mr,peak ≥ −16 mag. We find that plateau slope correlates with peak brightness, with many LLIIP SNe showing positive slopes—suggesting smaller progenitor radii and distinct density profiles compared to brighter Type IIP SNe. The plateau duration shows only a weak dependence on peak brightness, likely suggesting binary interaction. One SN exhibits a plateau-to-tail drop of &gt;3.5 mag, consistent with an electron-capture or failed SN with very low or zero nickel mass. We derive explosion and progenitor parameters of the entire Type IIP SN sample using semi-analytical and radiation-hydrodynamical models. Based on radiation-hydrodynamical model fitting, LLIIP SNe are characterized by low nickel masses (0.001─0.025 M⊙), low explosion energies (0.1─0.28 × 1051 erg), low ejecta masses ( 8.1−1.7+0.8  M⊙), and ZAMS masses below 11 M⊙. In comparison, the full Type IIP SN sample spans a wider range with nickel masses (0.001─0.222 M⊙), explosion energies (0.10-4.43 × 1051 erg), ejecta masses (5.4─24.8 M⊙), and ZAMS masses (9.3-16.7 M⊙). We find strong correlations between peak brightness, explosion energy, and nickel mass that extend to the low-luminosity end. We conclude that LLIIP SNe represent the faint, low-energy end of the Type IIP population and originate from the lowest-mass core-collapse progenitors.

Keywords: Core-collapse supernovae, Type II supernovae, Massive stars, Time domain astronomy, Supernovae, Stellar evolution
Four Cold Super-Jupiters Revealed by Extended and Complex Microlensing Signals. We present the analysis of four microlensing events, KMT-2020-BLG-0202, KMT-2022-BLG-1551, KMT-2023-BLG-0466, and KMT-2025-BLG-0121, which exhibit extended and complex anomalies in their light curves. These events were identified through a systematic reanalysis of KMTNet data aimed at detecting planetary signals that deviate from the typical short-term anomaly morphology. Detailed modeling indicates that all four anomalies were produced by planetary companions to low-mass stellar hosts. The events have mass ratios of q ∼ (5─14) × 10−3 and Einstein timescales of tE ∼ 20─43 days. Bayesian analyses based on Galactic models show that the companions are super-Jupiters with masses of a few to approximately 10 MJ, orbiting sub-solar-mass hosts located at distances of DL ∼ 4─7 kpc. All planets lie well beyond the snow line of their hosts, placing them in the regime of cold giant planets. These detections demonstrate that extended and complex microlensing anomalies, which are often challenging to recognize as planetary in origin, can nonetheless contain planetary signals. This work underscores the unique sensitivity of microlensing to cold, massive planets beyond the snow line and highlights the importance of systematic reanalyses of survey data for achieving a more complete and unbiased census of exoplanets in the Galaxy.

Keywords: Gravitational microlensing exoplanet detection
Photometric Analysis of the Interstellar Comet 3I/ATLAS During its Pre-perihelion Period. We present a photometric study of the interstellar comet 3I/ATLAS based on observations obtained between 2025 July 3 and September 22 from two observatories in Spain (Z10 and Y71) using small-aperture telescopes. The comet was monitored in five photometric bands (CV, C, R, G, and B), revealing an apparent brightness range from 19.10 to 13.50 mag. The observed variability reflects differences in observing site and filter bandpass, as well as significant scatter caused by background stellar contamination in crowded fields. Throughout the observing interval, comet 3I/ATLAS exhibited weak activity, with only a faint tail detected. A consistent brightening trend was measured in all filters, with average rates ranging from 0.033 to 0.066 magnitudes per day, indicating a progressive increase in activity. Measurements of coma size, tail length, and tail position angle were obtained for selected epochs. Derived Afρ values suggest that comet 3I/ATLAS was undergoing a phase of increasing activity associated with its approach to perihelion.

Keywords: Comet tails, Comet nuclei
Dynamical Interactions and Habitability in the TOI-700 Multi-planet System. The discovery of a second earth sized planet (TOI-700e) interior to the habitable candidate TOI-700d has prompted further research into this system, as the additional planet makes the TOI-700 system a tightly packed multi-planet system with multiple planets in the habitable zone, like TRAPPIST-1. In this work, we use the planetary evolution code VPLanet to assess the potential habitability of TOI-700d and TOI-700e. We first examine their orbital dynamics to evaluate the influence of planet─planet interactions on the planet spin, obliquity, and eccentricity. We then investigate whether these interactions are sufficient to cause either TOI-700d or e to be perturbed out of a habitable state, and whether we expect either planet could retain surface oceans over Gyr timescales. Together, these analyses allow us to assess the long-term habitability prospects of both TOI-700d and TOI-700e. We find that multi-planet interactions in the TOI-700 system do not prevent either planet from potentially retaining habitable conditions; however, we find that TOI-700e is located very near the boundary of the tidally locked habitable zone, suggesting further work is needed to determine whether it is truly habitable.

Keywords: Exoplanet evolution, Exoplanet surfaces, Habitable planets
Imaging Venus-like Worlds: Spectral, Polarimetric, and UV Diagnostics for the Habitable Worlds Observatory. Understanding planetary habitability requires a comparative approach that explores the divergent evolutionary outcomes of Earth and Venus. The Habitable Worlds Observatory (HWO) will be uniquely positioned to conduct a statistical and physical census of terrestrial exoplanets spanning the Venus Zone (VZ) and the Habitable Zone, enabling the detection and atmospheric characterization of post-runaway greenhouse worlds ("exoVenuses"). We present an updated list of VZ exoplanets, which raises the number of known candidates to 370. We describe a science case and an observing strategy for VZ exoplanets that integrates precursor exoplanet detection data and stellar characterization with HWO direct imaging, spectroscopy across the UV/optical/IR, and spectropolarimetry. Our proposed framework emphasizes a pathway toward the diagnosis of sulfur chemistry (SO2) and aerosol physics (H2SO4 clouds/hazes), planetary redox states (O2/O3 false positives from hydrogen loss), and cloud microphysics detection (rainbow polarization). We quantify implications for HWO requirements, including UV access to 0.2─0.4 μm, optical/NIR coverage to ≳1.5 μm, inner working angle (IWA) reaching 0.3─1.5 au around nearby Sun-like stars, and the SNR/resolution needed for key features. Finally, we outline a community-driven path to producing robust demographic inferences and target selection for optimizing HWO observations.

Keywords: Exoplanet atmospheric composition , Venus, Exoplanet systems, Exoplanet evolution, Astrobiology, Direct imaging, Habitable zone, Exoplanet atmospheres
Chasing the Tides: Searching for Orbital Decay Signatures in Transit Timing Data and Tidal Models for 20 Hot Jupiters. In this work, we present a transit timing variation analysis for 20 hot Jupiter systems, which we interpret with theoretical tidal dissipation models. For the majority of the sample, we conclude that a constant orbital period model represents the timing data best. Only WASP-12 b, TrES-1 b and WASP-121 b exhibit a changing orbital period, according to the most up-to-date results. We updated the orbital decay rate of WASP-12 b to  Ṗ=−29.4±4.0msyr−1  and the corresponding stellar tidal quality factor to  Q∗'=1.72±0.18×105 . For TrES-1 b, the median quadratic model suggests a period decrease at a rate of −14.9 ± 0.6 ms yr−1, but the corresponding  Q∗'=570±60  does not agree with the theoretical estimates, which suggest  Q∗'∼106  due to internal gravity wave dissipation. Lastly, WASP-121 b exhibits orbital growth at a rate of 15.1 ± 0.8 ms yr−1, and theoretical results support outward migration due to strong inertial wave dissipation.

Keywords: Hot Jupiters, Exoplanets, Transit timing variation method, Star-planet interactions, Tidal interaction