Sazuna/UAT_keywords huggingface dataset:
Exo-Dragonfly: Adapting the Dragonfly Telephoto Array to the Observation of Exoplanet Transits. We present the process and results of the Exo-Dragonfly project, an undertaking to adapt and use the Dragonfly Telephoto Array to observe exoplanet transit light curves. At the time of the project, the Dragonfly instrument, located in New Mexico, USA, was composed of 48 commercial 143 mm aperture telephoto lenses, split across two mounts and simultaneously observing the same field with r and g filters. The setup had a photon collection area equivalent to a 1 m diameter lens. With the driving goal of producing observations in support of the Transiting Exoplanet Survey Satellite follow-up efforts, we developed an automatic observation scheduling process, a new observing mode for time-sensitive time series observation, and a reduction/analysis pipeline to process data. Our results show that the Dragonfly Telephoto Array can achieve a photometric precision floor of ∼0.5 ppt for targets in the magnitude range of 8.5 ≲ mV ≲ 13 for 4–5 minutes bins. We discuss the successes and challenges encountered while using this unique multi-camera telescope as well as suggestions for improvements of this (or other similar) instruments as they pertain to exoplanet transit observations moving forward.

Keywords: Exoplanet detection methods, Transit photometry, Astronomical instrumentation
A "Rosetta Stone" for Studies of Spatial Variation in Astrophysical Data: Power Spectra, Semivariograms, Structure Functions, and More. From the turbulent interstellar medium to the cosmic web, astronomers in many different fields have needed to make sense of spatial data describing our Universe. Through different historical choices for mathematical conventions, many different subfields of spatial data analysis have evolved their own language for analysing structures and quantifying correlation in spatial data. Because of this history, terminology from a myriad of different fields is used, often to describe two data products that are mathematically identical. In this Note, we define and describe the differences and similarities between the power spectrum, the two-point correlation function, the covariance function, the semivariogram, and the structure functions, in an effort to unify the languages used to study spatial correlation. We also highlight under which conditions these data products are useful and describe how the results found using one method can be translated to those found using another, allowing for easier comparison between different subfields' native methods. We hope for this document to be a "Rosetta Stone" for translating between different statistical approaches, allowing results to be shared between researchers from different backgrounds, facilitating more cross-disciplinary approaches to data analysis.

Keywords: Astrostatistics tools, Astrostatistics techniques, Astrostatistics, Astrostatistics strategies
Cataclysmic Variables in Triples: Formation Models and New Discoveries. The formation of cataclysmic variables (CVs) has long been modeled as a product of common envelope evolution (CEE) in isolated binaries. However, a significant fraction of intermediate-mass stars—the progenitors of the white dwarfs (WDs) in CVs—are in triples. We therefore investigate the importance of triple star dynamics in CV formation. Using Gaia astrometry and existing CV catalogs, we construct a sample of ∼50 CVs in hierarchical triples within 1 kpc of the Sun, containing main-sequence and WD tertiaries at separations of 100–30,000 au. We infer that at least 10% of CVs host wide tertiaries. To interpret this discovery, we evolve a population of 2000 triples using detailed three-body simulations, 47 of which become CVs. We predict that 20% of CVs in triples form without ever experiencing CEE, where the WD and donor are brought together by the eccentric Kozai-Lidov mechanism after the formation of the WD. These systems favor larger donor stars and longer birth orbital periods (8–20 hr) than typical CVs. Among systems that do undergo CEE, about half would not have interacted without the presence of the tertiary. Triple formation channels both with and without CEE require initially wide inner orbits (≳1 au), which in turn require larger tertiary separations to be stable. Consistent with this prediction, we find that the observed Gaia CV triples have wider separations on average than normal wide binaries selected in the same way. Our work underscores the importance of triples in shaping interacting binary populations including CVs, ultracompact binaries, and low-mass X-ray binaries.

Keywords: Binary stars, White dwarf stars, Three-body problem, Trinary stars, Cataclysmic variable stars
A ZTF Search for Circumstellar Debris Transits in White Dwarfs: Six New Candidates, One with Gas Disk Emission, Identified in a Novel Metric Space. White dwarfs (WDs) showing transits from orbiting planetary debris provide significant insights into the structure and dynamics of debris disks, which are eventually accreted to produce metal pollution. This is a rare class of objects with only eight published systems. In this work, we perform a systematic search for such systems within 500 pc in the Gaia-eDR3 catalog of WDs using the light curves from the Zwicky Transient Facility (ZTF) and present six new candidates. Our selection process targets the top 1% most photometrically variable sources identified using a combined variability metric from ZTF and Gaia eDR3 photometry, boosted by a metric space we define using von Neumann statistics and Pearson-Skew as a novel discovery tool to identify these systems. This is followed by optical spectroscopic observations of visually selected variables to confirm metal pollution. Four of the six systems show long-timescale photometric variability spanning several months to years, resulting either from long-term evolution of transit activity or dust and debris clouds at wide orbits. Among them, WD J1013─0427 shows an indication of reddening during the long-duration dip. Interpreting this as dust extinction makes it the first system to indicate an abundance of dust grains with radius ≲0.3 μm in the occulting material. The same object also shows metal emission lines that map an optically thick eccentric gas disk orbiting within the star's Roche limit. For each candidate, we infer the abundances of the photospheric metals and estimate accretion rates. We show that transiting debris systems tend to have higher inferred accretion rates compared to the general population of metal-polluted WDs. Growing the number of these systems will further illuminate such comparative properties in the near future. Separately, we also serendipitously discovered an AM Canis Venaticorum showing a very long-duration outburst—only the fourth such system to be known.

Keywords: Transits, White dwarf stars, Variable stars, Debris disks, Circumstellar gas
WINTER on S250206dm: A Near-infrared Search for an Electromagnetic Counterpart to a Gravitational-wave Event. We present near-infrared follow-up observations of the International Gravitational Wave Network event S250206dm with the Wide-Field Infrared Transient Explorer (WINTER). Near-infrared observations are a critical component of electromagnetic follow-up to gravitational-wave events, as kilonovae are expected to exhibit long-lived emission at these wavelengths, especially from lanthanide-rich ejecta. WINTER is a near-infrared time-domain survey facility designed for EM follow-up of gravitational-wave sources, featuring a wide field of view (1.2 deg2), a dedicated 1 m robotic telescope, and coverage spanning 0.9─1.7 μm. S250206dm is the only neutron star merger in the fourth observing run, to date, localized to ≤300 deg2 with a False Alarm Rate below one per year, making it a particularly valuable target for follow-up. It has a 55% probability of being a neutron star-black hole merger and a 37% probability of being a binary neutron star merger. The event's estimated distance is 373 Mpc, with a 50% credible region spanning 38 deg2. WINTER covered 43% of the probability area at least once and 35% at least three times. Through automated and human candidate vetting, all transients were rejected as kilonova candidates. Given the large distance of the event, the WINTER upper limits do not place meaningful constraints on kilonova models. However, similar observations of future events-or in combination with optical surveys-can begin to exclude portions of the kilonova model space. This study highlights the promise of systematic infrared searches and the need for future wider and deeper infrared surveys.

Keywords: Gravitational wave astronomy, Time domain astronomy, Near infrared astronomy
Trumpler's Radial Velocities of Stars in Galactic Star Clusters<SUP></SUP>. We assess the accuracy of radial velocities of 671 stars located near Galactic clusters, measured by Robert Trumpler between 1924 and 1947 using the Lick Observatory 36 inch refractor equipped with prism spectrometers and photographic plates. We find that Trumpler's velocities share the same zero-point and scale as modern IAU radial velocity standards. Their accuracy ranges from 2 to 7 km s‑1, depending on stellar brightness, based on comparisons with new Doppler measurements from the Keck telescope and data from SIMBAD. We also provide improved star identifications, B-band photometry, and notes. A link is provided to an online PDF—previously available only in print—containing all 3782 of Trumpler's stellar radial velocities and associated Julian dates. These historical data can be combined with modern measurements to form a unique century-long baseline for detecting long-period stellar companions, gravitational perturbations from passing massive objects, and accelerations due to cluster and Galactic dynamics. *Based on observations at Lick and Keck Observatory.

Keywords: Astronomers, Astronomical techniques, Astrophysicists, Radial velocity, Catalogs, Star clusters
Inside the Iron Curtain: A Long Term Look at the Iron Stars XX Oph and AS 325. The Iron Stars XX Oph and AS 325, both binaries consisting of a Be + late K,M II star present remarkable optical spectra. Low velocity, dense winds from the late type star collide with high velocity, optically thin material expelled from the hot Be star producing a plethora of emission lines and complex P Cygni absorption profiles. The members of the American Association of Variable Star Observers have faithfully observed XX Oph for 85 yr and AS 325 for 32 yr. This long term photometric monitoring has revealed AS 325 to be an eclipsing system while XX Oph shows a complex light curve behavior. We present archival and recent photometry, new high-resolution optical imaging, and new high-resolution optical spectroscopy of the two stars. The orbital period of AS 325 is refined as 512.943 days and the stellar components are Be+K2.5 II. XX Oph is shown to be non-eclipsing and consists of Be+M6II stars.

Keywords: High resolution spectroscopy, Eclipses, Photometry, High angular resolution
A Hot Jupiter with a Retrograde Orbit Around A Sun-like Star and a Toy Model of Hot Jupiters in Wide Binary Star Systems. We report an observation of a transit of the hot Jupiter (HJ) KELT-23A b with the Keck Planet Finder spectrograph and a measurement of the sky-projected obliquity (λ) of its Sun-like (Teff ≍ 5900 K) host star. We measured a projected stellar obliquity of λ ≍ 180°, indicating that the orbit of the HJ is retrograde relative to the direction of the stellar spin. Due to the slow sky-projected rotational velocity of the host star ( vsini⋆≍0.5  km s−1), the true orbit of the HJ could be closer to polar. HJs around stars with effective temperatures below the Kraft break—such as KELT-23A—are generally found to have prograde orbits that are well-aligned with the equatorial planes of their host stars (i.e., λ ∼ 0°), most likely due to spin─orbit realignment driven by stellar tidal dissipation. This system is therefore a unique outlier that strains migration and tidal theories. The fact that the HJ has a highly misaligned orbit may suggest that the planet arrived at its close-in orbit relatively recently, possibly via interactions with the wide-separation (570 au) M-dwarf companion in the system, or that it has stalled near an antialigned or polar orientation while realigning. Using Gaia DR3, we determined the orbit of the stellar companion to be moderately face-on (γ = 60° ± 4°). We show that the distribution of observed systems in the γ─λ plane can be broadly reproduced using a toy model in which the orbits of the planetary and stellar companions begin aligned with the equatorial plane of the primary star and, upon migrating inwards, the planet preferentially obtains either an aligned or polar orbit.

Keywords: Exoplanet dynamics, Star-planet interactions, Exoplanet migration
Optimal Follow-up of Gravitational-wave Events with the UltraViolet EXplorer (UVEX). The UltraViolet EXplorer (UVEX) is a wide-field ultraviolet space telescope selected as a NASA Medium-Class Explorer mission for launch in 2030. UVEX will undertake deep, cadenced surveys of the entire sky to probe low mass galaxies and explore the ultraviolet (UV) time-domain sky, and it will carry the first rapidly deployable UV spectroscopic capability for a broad range of science applications. One of UVEX's prime objectives is to follow up gravitational wave (GW) binary neutron star mergers as targets of opportunity (ToOs), rapidly scanning across their localization regions to search for their kilonova (KN) counterparts. Early-time multiband ultraviolet light curves of KNe are key to explaining the interplay between jet and ejecta in binary neutron star mergers. Owing to high Galactic extinction in the ultraviolet and the variation of GW distance estimates over the sky, the sensitivity to kilonovae can vary significantly across the GW localization and even across the footprint of a single image given UVEX's large field of view. Good ToO observing strategies to trade off between area and depth are neither simple nor obvious. We present an optimal strategy for GW follow-up with UVEX in which exposure time is adjusted dynamically for each field individually to maximize the overall probability of detection. We model the scheduling problem using the expressive and powerful mathematical framework of mixed integer linear programming (MILP), and employ a state-of-the-art MILP solver to automatically generate observing plan timelines that achieve high probabilities of kilonova detection. We have implemented this strategy in an open-source astronomical scheduling software package called Multi-Mission Multi-Messenger Observation Planning Toolkit, on GitHub at https://github.com/m4opt/m4opt.

Keywords: Open source software, Wide-field telescopes, Ultraviolet observatories, Gravitational wave astronomy, Computational methods, Ultraviolet transient sources
Conditional Wavelet Diffusion Models for High-resolution Solar Spectra Reconstruction of CHASE Data. The high-resolution solar spectra are crucial for investigating solar activity, solar periodic variations and the underlying physical mechanisms of solar eruptions. The Chinese Hα Solar Explorer satellite observes the Sun from space, eliminating interference from Earth's atmosphere and weather conditions to ensure high observational accuracy and stability. However, limitations in observational resolution and technological constraints make the direct acquisition of high-resolution solar spectra a significant challenge. To address this challenge, a conditional wavelet diffusion model for high-resolution solar spectra reconstruction (CWDM-HRSSR) is proposed. Specifically, we apply the reverse Hilbert coding to convert both the residual and low-resolution spectra into two-dimensional spectral images, the residual spectral image serves as the target for the diffusion model, while the low-resolution spectral image acts as the conditional input. We propose dual-core wavelet pooling, which separately processes high-frequency and low-frequency components, and integrates them into the U-Net architecture of the diffusion model. Dual-core wavelet pooling effectively preserves low-frequency information while reducing interference from high-frequency noise. Additionally, by integrating a residual structure, we ensure that low-level features are shared with high-level representations, mitigating the risk of gradient vanishing in deep networks. Experimental results demonstrate that the generated high-resolution solar spectra closely resemble real solar spectra, confirming CWDM-HRSSR's superiority in detail reconstruction and accuracy.

Keywords: Astronomy databases, Neural networks, Astronomy data analysis, Solar flare spectra, Wavelet analysis
GReX: An Instrument Overview and New Upper Limits on the Galactic FRB Population. We present the instrument design and initial results for the Galactic Radio Explorer, an all-sky monitor for exceptionally bright transients in the radio sky. This instrument builds on the success of STARE2 to search for fast radio bursts (FRBs) from the Milky Way and its satellites. This instrument has deployments across the globe, with wide sky coverage and searching down to 32 μs time resolution, enabling the discovery of new super giant pulses. Presented here are the details of the hardware and software design of the instrument, performance in sensitivity and other key metrics, and experience in building a global-scale, low-cost experiment. We follow this discussion with experimental results on validation of the sensitivity via hydrogen-line measurements. We then update the rate of Galactic FRBs based on non-detection in the time since FRB 200428. Our results suggest FRB-like events are even rarer than initially implied by the detection of a MJy burst from SGR J1935+2154 in 2020 April.

Keywords: Radio bursts, Astronomical instrumentation
Probing the Atmospheric Precipitable Water Vapor with SOFIA. V. Telluric Scaling: Correcting Telescope Elevation Effects in Non-chopped Observations by Modeling the Telluric Background Based on the Water Vapor Overburden. We present a new data reduction technique for unchopped spectroscopic data developed for the Far-Infrared Field Integral Line Spectrometer instrument on-board the Stratospheric Observatory for Infrared Astronomy (SOFIA) to reduce spectral artifacts caused by large nod offsets. These large offsets are required to quantify the background without astronomical signal when large regions in the sky are mapped, e.g., in the Large Magellanic Cloud where reference beam offsets up to 1° can be needed. The technique uses the precipitable water vapor overburden derived from re-analyses from the European Centre for Medium-Range Weather Forecasts to determine the fraction of flux measured in each spatial and spectral pixel contributed by the atmospheric background. With that it is then possible to scale the reference measurement in the off beam to the sky elevation of the on source measurement. These large maps on SOFIA typically use the "on-the-fly" observing mode. The mode is highly efficient, but each point in the final map is integrated with multiple scans. Therefore artifacts from background subtraction do not only generate point by point offsets but can also degenerate the signal to noise ratio in each of the spectra since the sky background is often not spectrally flat.

Keywords: Astronomy data acquisition, Atmospheric extinction, Astronomy data analysis, Astronomical instrumentation, Astronomy data reduction
The Relationship Between X-Ray Binaries and Compact Star Clusters in NGC 2403, NGC 4303 and NGC 1672. This study investigates the identification X-ray binary systems (XRBs) and their association with nearby compact star clusters in the galaxies NGC 2403, NGC 4303, and NGC 1672. Using data from the Hubble Space Telescope (HST)/ACS/Wide Field Camera (WFC) and HST/WFC3/UVIS, we compiled a catalog of compact star clusters, identifying 541 in NGC 2403, 934 in NGC 4303, and 543 in NGC 1672. Archival Chandra data revealed 79 XRBs within the HST field of view across these galaxies. Optical counterparts were detected within an error radius at 2σ confidence levels for 26 of the 31 XRBs in NGC 2403, 15 of the 25 in NGC 4303, and 10 of the 23 in NGC 1672. We find that 66% of XRBs are associated with star clusters, with a fraction (49%) of high-mass XRBs (HMXBs) linked to young, compact clusters located within 200 pc in all three galaxies. Notably, in NGC 4303, five HMXBs are found within young clusters, while one low-mass XRB is located in an old cluster. Intermediate-mass XRBs (IMXBs) comprise about 45% of the XRB population in NGC 2403 and are predominantly found in the vicinity of young compact star clusters. A similar pattern is observed in the nearby galaxy NGC 4214, suggesting that the formation mechanisms of IMXBs may be more closely related to those of HMXBs.

Keywords: Extragalactic astronomy, X-ray binary stars, Star clusters
Fast Luminous Extragalactic Transients in the VLA Sky Survey: Implications for the Rates of Accretion-induced Collapse Events, Fast Blue Optical Transients and Gamma Ray Burst Afterglows. Radio wavelengths offer a unique window into high-energy astrophysical phenomena that may be obscured or too rapidly evolving to be captured at other wavelengths. Leveraging data from the Very Large Array Sky Survey, we perform a systematic search for fast (characteristic timescales ≲3 yr), luminous (L ≳ 1028 erg s−1 Hz−1) transients in the nearby universe (z ≤ 0.3). We report the discovery of five such transients, and classify them based on their synchrotron emission energetics and host galaxy properties. From this sample, we derive observational constraints on the volumetric rates of certain corresponding transient classes. We limit the rates of accretion-induced collapse of white dwarfs with dense circumstellar medium interaction (and those producing pulsar wind nebulae) at  ≲1.10−0.90+2.60 % ( ≲0.20−0.10+5.80 %) of the local Type Ia supernova rate, respectively, broadly consistent with theoretical predictions. For AT2018cow-like radio-bright luminous fast blue optical transients (LFBOTs), we estimate a rare occurrence rate of  ≲0.02−0.01+0.32 % of the local core-collapse supernova rate, which is at least an order of magnitude smaller than the estimates from optical searches, thus highlighting the rarity of radio-luminous LFBOTs. We constrain the local volumetric rates of long- and short-duration gamma-ray bursts (GRBs) to be  ≲11.46−9.48+26.28  Gpc−3 yr−1 and  ≲80.88−66.90+185.87  Gpc−3 yr−1, respectively, consistent with constraints from high energy and gravitational wave observations. These estimates incorporate beaming corrections, with median detectable viewing angles derived from afterglow simulations of ∼0.4 and ∼0.3 radians for long- and short-duration GRBs. Our findings highlight the potential of radio surveys to uncover rare, energetic transients. We emphasize the critical role of coordinated multi-wavelength follow-up in fully characterizing these enigmatic events.

Keywords: Gamma-ray bursts, Magnetars, Pulsar wind nebulae, Radio transient sources