Sazuna/UAT_keywords huggingface dataset:
Active Optical Control with Machine Learning: A Proof of Concept for the Vera C. Rubin Observatory. The Active Optics System of the Vera C. Rubin Observatory (Rubin) uses information provided by four wave front sensors to determine deviations between the reconstructed wave front and the ideal wave front. The observed deviations are used to adjust the control parameters of the optical system to maintain image quality across the 3°5 field of view. The baseline approach from the project is to obtain amplitudes of the Zernike polynomials describing the distorted wave front from out-of-focus images collected by the wave front sensors. These Zernike amplitudes are related via an "influence matrix" to the control parameters necessary to correct the wave front. In this paper, we use deep-learning methods to extract the control parameters directly from the images captured by the wave front sensors. Our neural net model uses anti-aliasing pooling to boost performance, and a domain-specific loss function to aid learning and generalization. The accuracy of the control parameters derived from our model exceeds Rubin requirements even in the presence of full-moon background levels and mis-centering of reference stars. Although the training process is time consuming, model evaluation requires only a few milliseconds. This low latency should allow for the correction of the optical configuration during the readout and slew interval between successive exposures.

Keywords: Observational astronomy, Neural networks, Convolutional neural networks, Astronomical optics, Multiple mirror telescopes, Optical telescopes, Astronomical instrumentation
A CO-to-H<SUB>2</SUB> Ratio of ≈10<SUP>-5</SUP> toward the Herbig Ae Star HK Ori. Measurements of gas mass in protoplanetary gas disks form the basis for estimating the conditions of planet formation. Among the most important constraints derived from disk diagnostics are the abundances of gas-phase species critical for understanding disk chemistry. Toward this end, we present direct line-of-sight measurements of H2 and CO, employing UV absorption spectroscopy from Hubble Space Telescope Cosmic Origins Spectrograph to characterize disk composition, molecular excitation temperatures, and spatial distribution in the circumstellar material around the Herbig Ae stars HK Ori and T Ori. We observe strong CO (N(CO) = 1015.5 cm-2; Trot(CO) = 19 K) and H2 (N(H2) = 1020.34 cm-2; Trot(H2) = 141 K) absorption toward HK Ori with a CO/H2 ratio of (≡N(CO)/N(H2)) = ${1.3}_{-0.7}^{+1.6}$ &lt;!-- --&gt; × 10-5. These measurements place direct empirical constraints on the CO-to-H2 conversion factor in the disk around a Herbig Ae star for the first time, although there is uncertainty concerning the exact viewing geometry of the disk. The spectra of T Ori show CO (N(CO) = 1014.9 cm-2; Trot(CO) = 124 K) absorption. Interestingly, we do not detect any H2 absorption toward this star (N(H2) &lt; 1015.9 cm-2). We discuss a potential scenario for the detection of CO without H2, which deserves further investigation. The low abundance ratio measured around HK Ori suggests significant depletion of CO in the circumstellar gas, which conforms with the handful of other recent CO abundance measurements in protoplanetary disks.

Keywords: Ultraviolet astronomy, Star formation, Circumstellar disks
Tails: Chasing Comets with the Zwicky Transient Facility and Deep Learning. We present Tails, an open-source deep-learning framework for the identification and localization of comets in the image data of the Zwicky Transient Facility (ZTF), a robotic optical time-domain survey currently in operation at the Palomar Observatory in California, USA. Tails employs a custom EfficientDet-based architecture and is capable of finding comets in single images in near real time, rather than requiring multiple epochs as with traditional methods. The system achieves state-of-the-art performance with 99% recall, a 0.01% false-positive rate, and a 1-2 pixel rms error in the predicted position. We report the initial results of the Tails efficiency evaluation in a production setting on the data of the ZTF Twilight survey, including the first AI-assisted discovery of a comet (C/2020 T2) and the recovery of a comet (P/2016 J3 = P/2021 A3).

Keywords: Astroinformatics, Comets, Convolutional neural networks, Astronomy data analysis
K2-138 g: Spitzer Spots a Sixth Planet for the Citizen Science System. K2 greatly extended Kepler's ability to find new planets, but it was typically limited to identifying transiting planets with orbital periods below 40 days. While analyzing K2 data through the Exoplanet Explorers project, citizen scientists helped discover one super-Earth and four sub-Neptune sized planets in the relatively bright (V = 12.21, K = 10.3) K2-138 system, all which orbit near 3:2 mean-motion resonances. The K2 light curve showed two additional transit events consistent with a sixth planet. Using Spitzer photometry, we validate the sixth planet's orbital period of 41.966 ± 0.006 days and measure a radius of ${3.44}_{-0.31}^{+0.32}\,{R}_{\oplus }$, solidifying K2-138 as the K2 system with the most currently known planets. There is a sizeable gap between the outer two planets, since the fifth planet in the system, K2-138 f, orbits at 12.76 days. We explore the possibility of additional nontransiting planets in the gap between f and g. Due to the relative brightness of the K2-138 host star, and the near resonance of the inner planets, K2-138 could be a key benchmark system for both radial velocity and transit-timing variation mass measurements, and indeed radial velocity masses for the inner four planets have already been obtained. With its five sub-Neptunes and one super-Earth, the K2-138 system provides a unique test bed for comparative atmospheric studies of warm to temperate planets of similar size, dynamical studies of near-resonant planets, and models of planet formation and migration.

Keywords: Mini Neptunes, Super Earths, Exoplanet systems, Exoplanets
Outbursting Young Stellar Object PGIR 20dci in the Perseus Arm. We report the discovery of a likely outbursting Class I young stellar object, associated with the star-forming region NGC 281-W (distance ∼2.8 kpc). The source is currently seen only at infrared wavelengths, appearing in both the Palomar Gattini InfraRed (1.2 μm) and the Near-Earth Object Wide-field Infrared Survey Explorer (3.4 and 4.6 μm) photometric time-domain surveys. Recent near-infrared imaging reveals a new, extended scattered light nebula. Recent near-infrared spectroscopy confirms the similarity of PGIR 20dci to FU Ori-type sources, based on strong molecular absorption in CO, H2O, and OH; weak absorption in several atomic lines; and a warm wind/outflow as indicated by a P Cygni profile in the He I λ10830 line. This is a rare case of an FU Ori star with a well-measured long-term photometric rise before a sharper outburst, and the second instance of an FU Ori star with a documented two-step brightening in the mid-infrared.

Keywords: Stellar accretion disks, Young stellar objects, Pre-main sequence stars, Circumstellar disks
Photometric and Spectroscopic Analysis of Four Contact Binaries. We present the photometric and spectroscopic analysis of four W UMa binaries J015829.5+260333 (hereinafter as J0158), J030505.1+293443 (hereinafter as J0305), J102211.7+310022 (hereinafter as J1022), and KW Psc. The VRcIc band photometric observations are carried out with the 1.3 m Devasthal Fast Optical Telescope (DFOT). For low-resolution spectroscopy, we used the 2 m Himalayan Chandra Telescope (HCT) as well as the archival data from the 4 m LAMOST survey. The systems J0158 and J0305 show a period increase rate of 5.26( ± 1.72) × 10-7 days yr-1 and 1.78( ± 1.52) × 10-6 days yr-1, respectively. The period of J1022 is found to be decreasing with a rate of 4.22 ( ± 1.67) × 10-6 days yr-1. The period analysis of KW Psc displays no change in its period. The PHOEBE package is used for the light-curve modeling and basic parameters are evaluated with the help of the GAIA parallax. The asymmetry of light curves is explained with the assumption of cool spots at specific positions on one of the components of the system. On the basis of temperatures, mass ratios, fill-out factors, and periods, the system J1022 is identified as a W-subtype system while the others show some mixed properties. To probe the chromospheric activities in these W UMa binaries, their spectra are compared with the known inactive stars' spectra. The comparison shows emission in Hα, Hβ, and Ca II. To understand the evolutionary status of these systems, the components are plotted in mass-radius and mass-luminosity planes with other well characterized binary systems. The secondary components of all the systems are away from ZAMS, which indicates that the secondary is more evolved than the primary component.

Keywords: Starspots, Photometry, Spectroscopy, Eclipsing binary stars, Contact binary stars
Longevity Is the Key Factor in the Search for Technosignatures. It is well known that the chances of success of the search for extraterrestrial intelligence depend on the longevity of technological civilizations or, more broadly, on the duration of the signs of their existence, or technosignatures. Here, we re-examine this general tenet in more detail, and we show that its broader implications have not been given their proper significance. In particular, an often overlooked aspect is that the duration of a technosignature is in principle almost entirely separable from the age of the civilization that produces it. We propose a classification scheme of technosignatures based on their duration, and we use Monte Carlo simulations to show that, given an initial generic distribution of Galactic technosignatures, only the ones with the longest duration are likely to be detected. This tells us, among other things, that looking for a large number of short-lived technosignatures is a weaker observational strategy than focusing the search on a few long-lived ones. It also suggests abandoning any anthropocentric bias in approaching the question of extraterrestrial intelligence. We finally give some ideas of possible pathways that can lead to the establishment of long-lived technosignatures.

Keywords: Search for extraterrestrial intelligence, Technosignatures, Astrobiology
On the Detection of Habitable Trojan Planets in the Kepler Circumbinary Systems. We present the results of a study of the prospect of detecting habitable Trojan planets in the Kepler Habitable Zone circumbinary planetary systems (Kepler-16, -47, -453, -1647, and -1661). We integrated the orbits of 10,000 separate N-body systems (N = 4, 6), each with a one Earth-mass body in a randomly selected orbit near the L4 and L5 Lagrangian points of the host HZ circumbinary planet. We find that stable Trojan planets are restricted to a narrow range of semimajor axes in all five systems and limited to small eccentricities in Kepler-16, -47, and -1661. To assess the prospect of the detection of these habitable Trojan planets, we calculated the amplitudes of the variations they cause in the transit timing of their host bodies. Results show that the mean amplitudes of the transit timing variations (TTVs) correlate with the mass of the transiting planet and range from 70 minutes for Kepler-16b to 390 minutes for Kepler-47c. Our analysis indicates that the TTVs of the circumbinary planets caused by these Trojan bodies fall within the detectable range of timing precision obtained from the Kepler telescope's long-cadence data. The latter points to Kepler data as a viable source to search for habitable Trojan planets.

Keywords: Transit timing variation method, N-body simulations, Trojan planets
Weather on Other Worlds. V. The Three Most Rapidly Rotating Ultra-cool Dwarfs. We present the discovery of rapid photometric variability in three ultra-cool dwarfs from long-duration monitoring with the Spitzer Space Telescope. The T7, L3.5, and L8 dwarfs have the shortest photometric periods known to date: ${1.080}_{-0.005}^{+0.004}$ hr, ${1.14}_{-0.01}^{+0.03}$ hr, and ${1.23}_{-0.01}^{+0.01}$ hr, respectively. We confirm the rapid rotation through moderate-resolution infrared spectroscopy, which reveals projected rotational velocities between 79 and 104 km s-1. We compare the near-infrared spectra to photospheric models to determine the objects' fundamental parameters and radial velocities. We find that the equatorial rotational velocities for all three objects are ≳100 km s-1. The three L and T dwarfs reported here are the most rapidly spinning and likely the most oblate field ultra-cool dwarfs known to date. Correspondingly, all three are excellent candidates for seeking auroral radio emission and net optical/infrared polarization. As of this writing, 78 L-, T-, and Y-dwarf rotation periods have now been measured. The clustering of the shortest rotation periods near 1 hr suggests that brown dwarfs are unlikely to spin much faster.

Keywords: Brown dwarfs, Variable stars, Spectroscopy, Stellar rotation, Infrared photometry
Search for Magnetic Accretion in SW Sextantis Systems. SW Sextantis systems are nova-like cataclysmic variables that have unusual spectroscopic properties, which are thought to be caused by an accretion geometry having part of the mass flux trajectory out of the orbital plane. Accretion onto a magnetic white dwarf is one of the proposed scenarios for these systems. To verify this possibility, we analyzed photometric and polarimetric time-series data for a sample of six SW Sex stars. We report possible modulated circular polarization in BO Cet, SW Sex, and UU Aqr with periods of 11.1, 41.2, and 25.7 minutes, respectively, and less significant periodicities for V380 Oph at 22 minutes and V442 Oph at 19.4 minutes. We confirm previous results that LS Peg shows variable circular polarization. However, we determine a period of 18.8 minutes, which is different from the earlier reported value. We interpret these periods as the spin periods of the white dwarfs. Our polarimetric results indicate that 15% of the SW Sex systems have direct evidence of magnetic accretion. We also discuss SW Sex objects within the perspective of being magnetic systems, considering the latest findings about the demography, formation, and evolution of cataclysmic variables.

Keywords: Photometry, Magnetic variable stars, Nova-like variable stars, Cataclysmic variable stars, Polarimetry
No Dependence of Radio Properties of Brightest Group Galaxies on the Luminosity Gap. We study the radio and optical properties of the brightest group galaxies (BGGs) in a sample of galaxy groups from the Sloan Digital Sky Survey (SDSS) DR7. The luminosity difference between the BGG and the second-ranked galaxy in the group (known as the luminosity, or magnitude, gap) has been used as a probe for the level of galaxy interaction for the BGG within the group. We study the properties of BGGs with magnitude gaps in the range of 0-2.7 mag, in order to investigate any relation between the luminosity gap and the radio properties of the BGG. In order to eliminate selection biases, we ensure that all variations in stellar mass are accounted for. We then confirm that, at fixed stellar mass, there are no significant variations in the optical properties of the BGGs over the full range of luminosity gaps studied. We compare these optical results with the Evolution and Assembly of GaLaxies and their Environments (EAGLE) hydrodynamical simulations and find broad consistency with the observational data. Using EAGLE we also confirm that no trends begin to arise in the simulated data at luminosity gaps beyond our observational limits. Finally, we find that, at a fixed stellar mass, the fraction of BGGs that are radio-loud also shows no trend as a function of luminosity gap. We examine how the BGG offset from the center of the group may affect the radio results and find no significant trend for the fraction of radio-loud BGGs with a magnitude gap in either the BGG samples with greater or less than 100 kpc offset from the center of the group.

Keywords: AGN host galaxies, Galaxy interactions, Radio continuum emission, Galaxy mergers, Radio active galactic nuclei
An Astronomical Image Content-based Recommendation System Using Combined Deep Learning Models in a Fully Unsupervised Mode. We have developed a method that maps large astronomical images onto a two-dimensional map and clusters them. A combination of various state-of-the-art machine-learning algorithms is used to develop a fully unsupervised image-quality assessment and clustering system. Our pipeline consists of a data pre-processing step where individual image objects are identified in a large astronomical image and converted to smaller pixel images. This data is then fed to a deep convolutional auto-encoder jointly trained with a self-organizing map (SOM). This part can be used as a recommendation system. The resulting output is eventually mapped onto a two-dimensional grid using a second, deep, SOM. We use data taken from ground-based telescopes and, as a case study, compare the system's ability and performance with the results obtained by supervised methods presented by Teimoorinia et al. The availability of target labels in this data allowed for a comprehensive performance comparison between our unsupervised and supervised methods. In addition to image-quality assessments performed in this project, our method can have various other applications. For example, it can help experts label images in a considerably shorter time with minimum human intervention. It can also be used as a content-based recommendation system capable of filtering images based on the desired content.

Keywords: Astronomy data modeling, Astronomy data analysis
Bioverse: A Simulation Framework to Assess the Statistical Power of Future Biosignature Surveys. Next-generation space observatories will conduct the first systematic surveys of terrestrial exoplanet atmospheres and search for evidence of life beyond Earth. While in-depth observations of the nearest habitable worlds may yield enticing results, there are fundamental questions about planetary habitability and evolution that can only be answered through population-level studies of dozens to hundreds of terrestrial planets. To determine the requirements for next-generation observatories to address these questions, we have developed Bioverse. Bioverse combines existing knowledge of exoplanet statistics with a survey simulation and hypothesis testing framework to determine whether proposed space-based direct imaging and transit-spectroscopy surveys will be capable of detecting various hypothetical statistical relationships between the properties of terrestrial exoplanets. Following a description of the code, we apply Bioverse to determine whether an ambitious direct imaging or transit survey would be able to determine the extent of the circumstellar habitable zone and study the evolution of Earth-like planets. Given recent evidence that Earth-sized habitable zone planets are likely much rarer than previously believed, we find that space missions with large search volumes will be necessary to study the population of terrestrial and habitable worlds. Moving forward, Bioverse provides a methodology for performing trade studies of future observatory concepts to maximize their ability to address population-level questions, including and beyond the specific examples explored here.

Keywords: Open source software, Exoplanets, Astrostatistics, Astrobiology, Exoplanet atmospheres
High-resolution CARMA Observation of Molecular Gas in the North America and Pelican Nebulae. In this paper, we present the first results from a CARMA high-resolution 12CO(1-0), 13CO(1-0), and C18O(1-0) molecular line survey of the North America and Pelican (NAP) Nebulae. CARMA observations have been combined with single-dish data from the Purple Mountain 13.7 m telescope, to add short spacings and to produce high-dynamic-range images. We find that the molecular gas is predominantly shaped by the W80 H II bubble, driven by an O star. Several bright rims noted in the observation are probably remnant molecular clouds, heated and stripped by the massive star. Matching these rims in molecular lines and optical images, we construct a model of the three-dimensional structure of the NAP complex. Two groups of molecular clumps/filaments are on the near side of the bubble: one is being pushed toward us, whereas the other is moving toward the bubble. Another group is on the far side of the bubble, and moving away. The young stellar objects in the Gulf region reside in three different clusters, each hosted by a cloud from one of the three molecular clump groups. Although all gas content in the NAP is impacted by feedback from the central O star, some regions show no signs of star formation, while other areas clearly exhibit star formation activity. Additional molecular gas being carved by feedback includes cometary structures in the Pelican Head region, and the boomerang features at the boundary of the Gulf region. The results show that the NAP complex is an ideal place for the study of feedback effects on star formation.

Keywords: Stellar feedback, Star forming regions, Massive stars, Molecular clouds, Photodissociation regions, Interstellar emissions, Radio telescopes, Star formation, Dust continuum emission, Young stellar objects, Radio interferometers, H II regions
A Gaussian Process Regression Reveals No Evidence for Planets Orbiting Kapteyn's Star. Radial-velocity (RV) planet searches are often polluted by signals caused by gas motion at the star's surface. Stellar activity can mimic or mask changes in the RVs caused by orbiting planets, resulting in false positives or missed detections. Here we use Gaussian process regression to disentangle the contradictory reports of planets versus rotation artifacts from Kapteyn's star. To model rotation, we use joint quasiperiodic kernels for the RV and Hα signals, requiring that their periods and correlation timescales be the same. We find that the rotation period of Kapteyn's star is 125 days, while the characteristic active-region lifetime is 694 days. Adding a planet to the RV model produces a best-fit orbital period of 100 yr, or 10 times the observing time baseline, indicating that the observed RVs are best explained by star rotation only. We also find no significant periodic signals in residual RV data sets constructed by subtracting off realizations of the best-fit rotation model and conclude that both previously reported "planets" are artifacts of the star's rotation and activity. Our results highlight the pitfalls of using sinusoids to model quasiperiodic rotation signals.

Keywords: Starspots, Exoplanet detection methods, Stellar activity, Gaussian Processes regression, Radial velocity, Stellar rotation