Sazuna/UAT_keywords huggingface dataset:
First Light with the 120-lens Dragonfly Spectral Line Mapper. The Dragonfly Spectral Line Mapper (DSLM) is a 120-lens distributed aperture narrowband imaging telescope that is operating as a pathfinder for an upcoming 1140-lens instrument being built to directly image the circumgalactic medium of nearby galaxies. DSLM has been on sky since 2023 October, collecting representative data for individual galaxies in Hα, [O III], and [N II]. In this paper, observations obtained for three targets (NGC 6946, NGC 891, and NGC 7479) are presented. These galaxies span a range of recessional velocities and foreground contamination levels, enabling a comprehensive evaluation of the experimental design. Diffuse Hα structures down to 10‑19 erg s‑1 cm‑2 arcsec‑2 on 10' scales are mapped by our data. We report the discovery of new extended structures in diffuse Hα and [N II] emission around NGC 6946 and NGC 891. We also map multiple new structures surrounding NGC 6946; however, due to the low recessional velocity of this object and the significant presence of galactic Hα emission at low galactic latitudes, we cannot confirm whether these gas clouds are associated with NGC 6946 or are of Galactic origin. We present a framework using the "sbcontrast" tool which can be broadly applied to evaluate the limiting depth of wide-field narrowband imaging observations. The surface brightness limits obtained with DSLM are consistent with our theoretical predictions and, in fields with low foreground contamination, the imaging depth is not limited by instrument systematics. Future dedicated surveys on galaxies selected by recessional velocity to avoid sky emission lines are projected to reach surface brightness limits of 10‑20 erg s‑1 cm‑2 arcsec‑2 on scales of a few arcmin, placing the circumgalactic medium of nearby galaxies within reach.

Keywords: Optical telescopes, Circumgalactic medium
Correlation Between Outlying Halo Abundance and Host Halo Properties. The correlations between dark matter halo properties and subhalo abundance, or occupation, have been studied extensively; however, existing studies have mainly focused on subhalos within the virial radius of the host halo. In this work, we quantify the correlation between host halo properties and the abundance of neighboring halos that reside right outside of the virial radius of the host halos. We compute the correlations between four host halo properties (half-mass scale, concentration, peak-mass scale, and spin) and the outlying halo occupation out to 1.5 Mpc for Milky Way-mass host halos, and study how the correlation strength varies with radius. We also investigate if the outlying halo occupation can provide information about the host halo properties. We find that host halo properties impact the neighboring halo abundance beyond the virial radius, and the locations at which the correlation peaks do not typically align with the virial radius or splashback radius. The behavior of this observed correlation as a function of radius, especially in the outskirts, is connected to the effect of halo assembly bias. However, there is no universal behavior when considering different host halo properties. Our results are the first to quantify the occupation variation of outlying halos beyond the virial radius. They provide the theoretical background for interpreting the observed satellite systems when the observed satellites are not strictly defined to be within the virial radius.

Keywords: Galaxy dark matter halos, Dark matter distribution, Galaxy groups, Galaxy counts, N-body simulations
IIb or not IIb: A Catalog of ZTF Kilonova Imposters. Among the various classes of fast optical transients (FOTs), kilonovae (KNe), which can emerge as a result of neutron star mergers, are extremely challenging to observe because of not only the rapid timescale on which they fade (on the order of days), but also due to the relative scarcity of their occurrence. This scarcity is compounded by the large number of other FOTs that may initially resemble the characteristic rise of a KNe. While these objects can be ruled out as candidate KNe by taking spectroscopy, a method of confidently ruling out transients based on photometric analysis alone would be incredibly valuable. We describe the compilation of various "imposter" transients, including a plurality of IIb SNe, and investigate a number of comparative metrics by which one might be able to remove transients from consideration without the use of spectroscopy. We provide a list of these objects and their classifications as well as a glossary of the transient types included in the sample.

Keywords: Neutron stars, Gamma-ray bursts, Astronomy databases, Compact binary stars, Astronomy data analysis, Gravitational wave sources, Extragalactic astronomy, Gamma-ray transient sources, Supernovae
BSN-III: The First Multiband Photometric Study on the Eight Total Eclipse Contact Binary Stars. This study continues our in-depth investigation of total-eclipse W Ursae Majoris-type contact binaries by analyzing eight new systems, complementing our previous work. Multiband BVRcIc photometric data were acquired through ground-based observations at an observatory in Mexico, from which new times of minima were determined. Our analysis of orbital period variations using the O ‑ C method revealed that one system shows no long-term variation, four systems exhibit a secular decrease in their orbital periods, and two systems exhibit a secular increase, suggesting mass transfer between the components. Notably, one system displays a cyclic variation with an amplitude of 0.00865 days and a period of 10.49 yr, which we attribute to the light travel time effect induced by a tertiary companion, possibly a brown dwarf. We modeled the light curves using the PHysics Of Eclipsing BinariEs Python code. Six of the target systems required the inclusion of a cold starspot on one of the system's stars due to the asymmetry observed in the maxima of their light curves. Absolute parameters were estimated using the Gaia DR3 parallax method. Using the components' effective temperatures and masses, we classified five of the systems as W-subtype and three as A-subtype. The stellar evolution was illustrated through the mass–radius and mass–luminosity diagrams. Furthermore, we investigated the dynamical stability of two systems with extremely low mass ratios.

Keywords: Eclipsing binary stars, Astronomy data analysis, Fundamental parameters of stars, Close binary stars
Constraining the Nature and Long-term Stability of FRB 20121102A's Persistent Radio Source. The persistent radio source (PRS) associated with FRB 20121102A, the first precisely localized repeating fast radio burst (FRB), provides key constraints on both its local environment and the nature of the underlying FRB engine. We present a seven-year (2016─2023) temporal analysis of the PRS, combining new uGMRT observations with archival data across L-band frequencies. We find no statistically significant long-term trend in its L-band flux density. The observed variability is consistent with refractive interstellar scintillation, and the data do not require the PRS to be a source exhibiting strong intrinsic variability. This stability challenges models predicting rapid fading from evolving magnetized outflows, such as those powered by young magnetars or relativistic shocks. Our low-frequency observations show no evidence for spectral evolution between 1.4 GHz and 745 MHz, with a measured spectral index of α = −0.15 ± 0.08, in agreement with values reported from earlier observations in 2016─2017. The PRS remains compact, exhibits a flat radio spectrum, and—if powered by an intermediate-mass black hole accreting at a low Eddington ratio—its radio and X-ray properties are broadly consistent with the fundamental plane of radio-loud AGNs. While not conclusive, this scenario represents a viable alternative to magnetar wind nebula models and warrants further investigation. Furthermore, we find no statistically significant correlation between FRB burst activity and the luminosity of associated PRSs among repeating sources. This apparent decoupling challenges simple progenitor models that directly link bursts and persistent emission. Together, these results suggest that the FRB engine and PRS may in some systems originate from physically distinct sources, underscoring the need for flexible models to explain the diverse environments of repeating FRBs.

Keywords: Neutron stars, Magnetars, AGN host galaxies, Radio transient sources
Experimental Validation for Serial Conjunction of Diffraction-limited Coronagraph and Fiber Nuller. We report the experimental results of a serially conjoined nuller system, which combines a type of Lyot coronagraph with a fiber nuller. The utilized one-dimensional diffraction-limited coronagraph (1DDLC) has promising features (binary nuller, small inner working angles). Still, it has a performance that is highly sensitive to spectral bandwidth and tilt aberrations. Nevertheless, for the 1DDLC, wavelengths other than the design wavelength introduce leaks with a flat wavefront on the Lyot-stop plane, preserving the same complex amplitude profile as an on-axis point source. This property supports the concept of serially coupling additional nullers after the 1DDLC. The fiber-nulling unit employs a Lyot-plane mask, relay optics (1/100×), and a single-mode fiber. The Lyot-plane mask splits the incoming beam-comprising leakage from the 1DDLC and planetary light-into four beams so that, in principle, the on-axis single-mode fiber does not couple with the on-axis leak from the 1DDLC. For the wavelength 6% less than the coronagraph's design-center wavelength, we confirmed the contrast mitigation ability of 3.5 × 10‑5, which is about 1/20 times the value of the case with only 1DDLC. The resultant value approximately reaches the 1DDLC's contrast mitigation ability at the design center wavelength demonstrated in the previous study, suggesting that the combined system works robustly against the broad spectral bandwidth. Future work needs to address the demonstration of the anticipated robustness for the contrast-mitigation level lower than about 10‑5.

Keywords: Coronagraphic imaging, Astrobiology, Direct imaging, Exoplanets
Development of a New Ground-based Instrumentation Technique for Low-resolution Exoplanet Transmission Spectroscopy. We present a new instrumentation technique for high-precision, ground-based spectrophotometric measurements ideal for low-resolution (R ∼ 20–60) exoplanet transmission spectroscopy. This technique employs novel thin-film coating technology for wide-band, simultaneous multi-band imaging, enabling high-precision differential photometry through self-referencing and comparison stars. Theoretical calculations and on-sky results show that this method effectively reduces 96% of amplitude scintillation noise and other systematics that typically limit ground-based spectrophotometric precision for bright stars. On-sky results are demonstrated using the custom-built Exoplanet Transmission Spectroscopy Imager (ETSI), deployed at the McDonald Observatory 2.1 m telescope in 2022. For a V = 9.7 mag star, ETSI achieves a spectrophotometric precision of 50 ppm in a 40 nm band over 1.0 hr, below the atmospheric scintillation noise floor. Using ETSI, we present a measured transmission spectrum of the hot Saturn HAT-P-44Bb to demonstrate the technique's application. We perform a basic spectral retrieval to verify the measurement's consistency with the planet's known or expected physical parameters. Future deployment of this technique in instruments on mid to large-class observatories could enable the ability to characterize hundreds of exoplanet atmospheres in the visible with low resolution transmission spectroscopy.

Keywords: Astronomical instrumentation, Exoplanet atmospheres
Prospects of Detecting Rotational Flatness of Exoplanets from Space-based Photometry. In the era of photometry with space-based telescopes, such as CHaracterizing ExOPlanets Satellite, James Webb Space Telescope, PLAnetary Transits and Oscillations of stars, and Atmospheric Remote-sensing Infrared Exoplanet Large-survey, the road has opened for detecting subtle distortions in exoplanet transit light curves-resulting from their non-spherical shape. We investigate the prospects of retrieval of rotational flatness (oblateness) of exoplanets at various noise levels. We present a novel method for calculating the transit light curves based on the Gauss–Legendre quadrature. We compare it in the non-rotating limit to the available analytical models. We conduct injection-and-retrieval tests to assess the precision and accuracy of the retrievable oblateness values. We find that the light curve calculation technique is about 25% faster than a well-known analytical counterpart, while still being precise enough. We show that a 3σ oblateness detection is possible for a planet orbiting bright enough stars, by exploiting a precise estimate on the stellar density obtained e.g., from asteroseismology. We also show that for noise levels ≥256 ppm (expressed as point-to-point scatter with a 60 s exposure time) detection of planetary oblateness is not reliable.

Keywords: Transit photometry, Astronomy data analysis, Oblateness, Exoplanets
Theoretical Mass Function for Secondaries Forming via Gravitational Instability in Circumstellar Disks. This paper constructs a theoretical framework for calculating the distribution of masses for secondary bodies forming via gravitational instability in the outer regions of circumstellar disks. We show that several alternate ways to specify the mass scale of forming objects converge to the same result under the constraint that the parental disks are marginally stable with stability parameter Q = 1. Next we show that the well-known constraint that the formation of secondary bodies requires rapid cooling is equivalent to that of opacity limited fragmentation. These results are then used to derive a mass function for secondary objects forming through disk instability. The resulting distribution is relatively narrow, with log-normal-like shape, a characteristic mass scale of order MP ∼ 10MJup, and an approximate range of 4‑80MJup. Current estimates for the occurrence rate suggest that these objects are outnumbered by both stars and planets formed via core accretion.

Keywords: Solar system formation, Protoplanetary disks, Planet formation
A Morphological Model to Separate Resolved─Unresolved Sources in the DESI Legacy Surveys: Application in the LS4 Alert Stream. Separating resolved and unresolved sources in large imaging surveys is a fundamental step to enable downstream science, such as searching for extragalactic transients in wide-field time-domain surveys. Here we present our method to effectively separate point sources from the resolved, extended sources in the Dark Energy Spectroscopic Instrument (DESI) Legacy Surveys (LS). We develop a supervised machine learning model based on the Gradient Boosting algorithm XGBoost. The features input to the model are purely morphological and are derived from the tabulated LS data products. We train the model using ∼2 × 105 LS sources in the COSMOS field with HST morphological labels and evaluate the model performance on LS sources with spectroscopic classification from the DESI Data Release 1 (∼2 × 107 objects) and the Sloan Digital Sky Survey Data Release 17 (∼3 × 106 objects), as well as on ∼2 × 108 Gaia stars. A significant fraction of LS sources are not observed in every LS filter, and we therefore build a "Hybrid" model as a linear combination of two XGBoost models, each containing features combining aperture flux measurements from the "blue" (gr) and "red" (iz) filters. The Hybrid model shows a reasonable balance between sensitivity and robustness, and achieves higher accuracy and flexibility compared to the LS morphological typing. With the Hybrid model, we provide classification scores for ∼3 × 109 LS sources, making this the largest ever machine learning catalog separating resolved and unresolved sources. The catalog has been incorporated into the real-time pipeline of the La Silla Schmidt Southern Survey (LS4), enabling the identification of extragalactic transients within the LS4 alert stream.

Keywords: Surveys, Classification, Catalogs, Astrostatistics
Co-phase Detection for Segmented Mirrors: Using a New Type of Edge Sensor Based on Fringes of Equal Thickness. The edge sensor constitutes a critical component in the co-phase system of the large-aperture optical astronomical segmented mirror telescopes. Presently, electric edge sensors are commonly employed across various segmented telescopes, offering high precision. However, phenomena such as temperature and temporal drifts pose challenges, restricting their deployment in demanding environments. Our team developed a unique optical edge sensor based on fringes of equal thickness to circumvent these restrictions. This edge sensor can overcome these difficulties and provide high precision in the co-phase detection of segmented mirrors. The study presents both simulation and experimental findings about the performance of this edge sensor in co-phase detection. Results demonstrate that, in laboratory experiments, the maximum absolute error for this edge sensor prototype is 5 nm, satisfying the stringent requirements for the large-aperture segmented mirror telescopes.

Keywords: Optical interferometry, Astronomical techniques, Astronomical instrumentation
Using the Antenna Impedance to Estimate Soil Electrical Parameters for the MIST Global 21 cm Experiment. Radio experiments trying to detect the global 21 cm signal from the early Universe are very sensitive to the electrical properties of their environment. For ground-based experiments with the antenna above the soil it is critical to characterize the effect from the soil on the sky observations. This characterization requires estimating the soil's electrical conductivity and relative permittivity in the same frequency range as the observations. Here we present our initial effort to estimate the conductivity and relative permittivity of the soil using the impedance of an antenna mounted at a distance above the surface. In this technique, the antenna used for soil characterization is the same as the antenna used for sky observations. To demonstrate the technique we use the antenna of the MIST global 21 cm experiment. We measured the antenna impedance at three sites in the Greater Concepción area, Chile. The measurements were done between 25 and 125 MHz, matching the range used by MIST for sky observations. The soil parameters were estimated by fitting the impedance measurements with electromagnetic simulations of the antenna and soil. In this initial effort the soil was modeled as homogeneous. The conductivity at the three sites was found to be between 0.007 and 0.049 Sm‑1, and the relative permittivity between 1.6 and 12.7. The percent precision of the estimates at 68% probability is, with one exception, better (lower) than 33%. The best-fit simulations have a better than 10% agreement with the measurements relative to the peak values of the resistance and reactance across our frequency range. For MIST, these results represent a successful proof of concept of the use of the antenna impedance for soil characterization, and are expected to significantly improve in future implementations.

Keywords: Early universe, Calibration, Radio receivers, Astronomical instrumentation, Intergalactic medium
STag. II. Classification of Serendipitous Supernovae Observed by Galaxy Redshift Surveys. With the number of supernovae observed expected to drastically increase thanks to large-scale surveys like the Dark Energy Spectroscopic Instrument (DESI), it is necessary that the tools we use to classify these objects keep up with this increase. We previously created Supernova Tagging and Classification (STag) to address this problem by employing machine learning techniques alongside logistic regression in order to assign "tags" to spectra based on spectral features. STag II is a continuation of this work, which now makes use of model supernova spectra combined with real DESI spectra in order to train STag to better deal with realistic data. We also make use of the rlap score as a trustworthiness cut, making for a more robust and accurate supernova classifier than before.

Keywords: Astrostatistics techniques, Supernovae, Classification
Twin Peaks: SN 2021uvy and SN 2022hgk in the Landscape of Double-peaked Stripped Envelope Supernovae. In recent years, a class of stripped-envelope supernovae (SESNe) has emerged that show two distinct peaks in their light curves, where the first peak cannot be attributed to shock cooling emission. Such peculiar supernovae are often studied individually, explained by invoking some combination of powering mechanisms. However, they have seldom been discussed in the broader context of double-peaked SESNe. In this paper, we attempt to form a picture of the landscape of double-peaked SESNe and their powering mechanisms by adding two more objects—SN 2021uvy and SN 2022hgk. SN 2021uvy is a broad and luminous SN Ib with an unusually long rise of the first peak and constant color evolution with rising photospheric temperature during the second peak. Although its first peak is similar to that of SN 2019stc, their second peaks differ in properties, making it unique among double-peaked objects. SN 2022hgk shows striking photometric similarity to SN 2019cad and spectroscopic similarity to SN 2005bf, both of which have been suggested to be powered by a double-nickel distribution in their ejecta. We analyze their light curves and colors, compare them with a sample of other double-peaked published supernovae for which we have additional data, and analyze the light curve parameters of the sample. We observe a correlation (p-value ∼ 0.025) between the peak absolute magnitudes of the first and second peaks. The sample shows variety in the photometric and spectroscopic properties, and thus no single definitive powering mechanism applies to the whole sample. However, sub-groups of similarity exist that can be explained by mechanisms like the double-nickel distribution, magnetar central engine, interaction, and fallback accretion. We also map out the duration between the peaks (∆t21) versus the difference between peak absolute magnitudes (∆M21) as a phase-space that could potentially delineate the most promising powering mechanisms for the double-peaked SESNe.

Keywords: Type Ib supernovae, Type Ic supernovae, Core-collapse supernovae
10,000 Resolved Triples from Gaia: Empirical Constraints on Triple Star Populations. We present a catalog of ∼10,000 resolved triple star systems within 500 pc of the Sun, constructed using Gaia data. The triples include main-sequence, red giant, and white dwarf components spanning separations of 10–50,000 au. A well-characterized selection function allows us to constrain intrinsic demographics of the triple star population. We find that (a) all systems are compatible with being hierarchical and dynamically stable; (b) mutual orbital inclinations are isotropic for wide triples but show modest alignment as the systems become more compact; (c) primary masses follow a Kroupa initial mass function weighted by the triple fraction; (d) inner binary orbital periods, eccentricities, and mass ratios mirror those of isolated binaries, including a pronounced twin excess (mass ratios greater than 0.95) out to separations of 1000+ au, suggesting a common formation pathway; (e) tertiary mass ratios follow a power-law distribution with slope ‑1.4; (f) tertiary orbits are consistent with a log-normal period distribution and thermal eccentricities, subject to dynamical stability. Informed by these observations, we develop a publicly available prescription for generating mock triple star populations. Finally, we estimate the catalog's completeness and infer the intrinsic triple fraction, which rises steadily with primary mass: from 5% at ≲0.5 M⊙ to 35% at 2 M⊙. The public catalog provides a robust testbed for models of triple star formation and evolution.

Keywords: Binary stars, Star formation, Three-body problem, Trinary stars, Stellar evolution