Sazuna/UAT_keywords huggingface dataset:
Precise Estimation of Source Intensity for Wide-field Telescopes with PSF Modeling. Wide-field small aperture optical telescopes are widely used in large-scale surveys currently and they have made great contributions in a number of astronomical applications. However, specific challenges arise owing to the defects caused by the optical system, and the image quality and reduction precision are negatively affected. An innovative method is proposed to address these challenges and achieve a high-precision source intensity estimation. In implementation, first a dedicated pipeline is developed to investigate the point-spread function (PSF) components from large amounts of images, using principal component analysis. Then the PSF model that reveals the actual characteristics of the optical system is constructed based on the evaluation. Last the equations for centroid and intensity estimation are constructed and the results are obtained. A trial of observations is performed with a wide-field small aperture telescope, and a large number of raw images, as well as simulated images, are acquired to test the efficiency of our method. The intensity measurement is performed with our method and other common algorithms, including the modified moment, Gaussian fitting, and SExtractor. Based on the comparison it is demonstrated that our proposed method outperforms the others. The results indicate that our method explores the limitations of such a system and additional gains can be achieved in wider applications.

Keywords: CCD observation, Magnitude, Astronomical techniques, Astrometry, Photometry
Following Up the Kepler Field: Masses of Targets for Transit Timing and Atmospheric Characterization. We identify a set of planetary systems observed by Kepler that merit transit-timing variation (TTV) analysis given the orbital periods of transiting planets, the uncertainties for their transit times, and the number of transits observed during the Kepler mission. We confirm the planetary nature of four Kepler Objects of Interest within multicandidate systems. We forward-model each of the planetary systems identified to determine which systems are likely to yield mass constraints that may be significantly improved upon with follow-up transit observations. We find projected TTVs diverge by more than 90 minutes after 6000 days in 27 systems, including 22 planets with orbital periods exceeding 25 days. Such targets would benefit the most from additional transit-timing data. TTV follow-up could push exoplanet characterization to lower masses, at greater orbital periods and at cooler equilibrium temperatures than is currently possible from the Kepler data set alone. Combining TTVs and recently revised stellar parameters, we characterize an ensemble of homogeneously selected planets and identify planets in the Kepler field with large-enough estimated transmission annuli for atmospheric characterization with James Webb Space Telescope.

Keywords: Transit timing variation method, Exoplanet systems
NEMESIS: Exoplanet Transit Survey of Nearby M-dwarfs in TESS FFIs. I.. In this work, we present an analysis of 33,054 M-dwarf stars, located within 100 parsecs, via the Transiting Exoplanet Survey Satellite (TESS) full-frame images (FFIs) of observed sectors 1-5. We present a new pipeline called NEMESIS, developed to extract detrended photometry, and to perform transit searches of single-sector data in TESS FFIs. As many M-dwarfs are faint, and are not observed with a two-minute cadence by TESS, FFI transit surveys can provide an empirical validation of how many planets are missed, using the 30-minute cadence data. In this work, we detect 183 threshold crossing events, and present 29 candidate planets for sectors 1-5, 24 of which are new detections. Our sample contains orbital periods ranging from 1.25 to 6.84 days, and planetary radii from 1.26 to 5.31 R⊕. With the addition of our new planet candidate detections, along with detections previously observed in sectors 1-5, we calculate an integrated occurrence rate of 2.49 ± 1.58 planets per star, for the period range ∈ [1, 9] days, and planet radius range ∈ [0.5,11] R⊕. We project an estimated yield of 122 ± 11 transit detections of nearby M-dwarfs. Of our new candidates, 23 have signal-to-noise ratios &gt;7, transmission spectroscopy metrics &gt;38, and emission spectroscopy metrics &gt;10. We present all of our data products for our planet candidates via the Filtergraph data visualization service, located at https://filtergraph.com/NEMESIS.

Keywords: M dwarf stars, M stars, Exoplanet astronomy, Exoplanet detection methods, Transit photometry
The Detection and Characterization of Be+sdO Binaries from HST/STIS FUV Spectroscopy. The B emission-line stars are rapid rotators that were probably spun up by mass and angular momentum accretion through mass transfer in an interacting binary. Mass transfer will strip the donor star of its envelope to create a small and hot subdwarf remnant. Here we report on Hubble Space Telescope/STIS far-ultraviolet spectroscopy of a sample of Be stars that reveals the presence of the hot sdO companion through the calculation of cross-correlation functions of the observed and model spectra. We clearly detect the spectral signature of the sdO star in 10 of the 13 stars in the sample, and the spectral signals indicate that the sdO stars are hot, relatively faint, and slowly rotating as predicted by models. A comparison of their temperatures and radii with evolutionary tracks indicates that the sdO stars occupy the relatively long-lived, He-core burning stage. Only 1 of the 10 detections was a known binary prior to this investigation, which emphasizes the difficulty of finding such Be+sdO binaries through optical spectroscopy. However, these results and others indicate that many Be stars probably host hot subdwarf companions.

Keywords: Spectroscopic binary stars, Emission line stars, Stellar evolution
A Careful Reassessment of Globular Cluster Multiple Population Radial Distributions with Sloan Digital Sky Survey and Johnson-Cousins Broadband Photometry. Inconsistencies regarding the nature of globular cluster (GC) multiple population radial distributions is a matter for concern given their role in testing or validating cluster dynamical evolution modeling. In this study, we present a reanalysis of eight GC radial distributions using publicly available ground-based ugriz and UBVRI photometry; correcting for a systematic error identified in the literature. We detail the need for including and considering not only Kolmogorov-Smirnov (K-S) probabilities but critical K-S statistic values as well when drawing conclusions from radial distributions, as well as the impact of sample incompleteness. Revised cumulative radial distributions are presented, and the literature of each cluster is reviewed to provide a fuller picture of our results. We find that many multiple populations are not as segregated as once thought, and that there is a pressing need for better understanding of the spatial distributions of multiple populations in GCs.

Keywords: Globular star clusters, Hertzsprung Russell diagram, Red giant branch, Broad band photometry, Dynamical evolution
Broadband Stability of the Habitable Zone Planet Finder Fabry-Pérot Etalon Calibration System: Evidence for Chromatic Variation. The comblike spectrum of a white light-illuminated Fabry-Pérot etalon can serve as a cost-effective and stable reference for precise Doppler measurements. Understanding the stability of these devices across their broad (hundreds of nanometers) spectral bandwidths is essential to realizing their full potential as Doppler calibrators. However, published descriptions remain limited to small bandwidths or short time spans. We present an ∼6 month broadband stability monitoring campaign of the Fabry-Pérot etalon system deployed with the near-infrared Habitable Zone Planet Finder (HPF) spectrograph. We monitor the wavelengths of each of ∼3500 resonant modes measured in HPF spectra of this Fabry-Pérot etalon (free spectral range = 30 GHz, bandwidth = 820-1280 nm), leveraging the accuracy and precision of an electro-optic frequency comb reference. These results reveal chromatic structure in the Fabry-Pérot mode locations and their evolution with time. We measure an average drift on the order of 2 cm s-1 day-1, with local departures up to ±5 cm s-1 day-1. We discuss these behaviors in the context of the Fabry-Pérot etalon mirror dispersion and other optical properties of the system and the implications for the use of similar systems for precise Doppler measurements. Our results show that this system supports the wavelength calibration of HPF at the ≲10 cm s-1 level over a night and the ≲30 cm s-1 level over ∼10 days. Our results also highlight the need for long-term and spectrally resolved study of similar systems that will be deployed to support Doppler measurement precision approaching ∼10 cm s-1.

Keywords: Exoplanet detection methods, Spectroscopy, Fabry-Perot interferometers, Radial velocity, Near infrared astronomy
Speckle Interferometry at the OAN-SPM México: Multiband Astrometry of Double Stars Measured in 2018 and 2019. In this paper we present multiband speckle interferometric measurements of double stars performed at the 2.1 m telescope of the Observatorio Astronómico Nacional, San Pedro Mártir, México. We focused our efforts on objects from the Washington Double Star Catalog that were observed during five runs allocated in 2018 and 2019. We report here 2101 astrometric and 2027 photometric measurements of 631 pairs, with angular separations ranging from 0"05 to 6"09, including 1622 measurements with separations smaller than 1″, and a magnitude difference up to 5.99 mag through the V filter, 5.46 mag for the R filter, and 5.85 mag for the I filter. We estimated a mean error in separation of 12 mas, 1°1 in position angle, and 0.14 mag for the magnitude difference. We confirmed 58 double stars discovered by Hipparcos. For the first time we are presenting astrometric measurements for 7 systems listed at the Washington Double Star Catalog as being suspected binaries, which did not have a secondary confirmation, and 15 stars with only one published measurement. We identified a new close companion with a mean angular separation of 0"10, detected in a previously known pair. Finally, we present a correction to two previously published orbital solutions of two visual binaries.

Keywords: Close binary stars, Angular separation, Astrometry, Speckle interferometry, Interferometric binary stars, Visual binary stars
The APOGEE Data Release 16 Spectral Line List. The updated H-band spectral-line list (from λ15000-17000) adopted by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) for the SDSS-IV Data Release 16 (DR16) is presented in this work. The APOGEE line list is a combination of atomic and molecular lines, with data drawn from laboratory, theoretical, and astrophysical sources. Oscillator strengths and damping constants are adjusted using high signal-to-noise, high-resolution spectra of the Sun, and α Boo (Arcturus), as "standard stars." Updates to the DR16 line list, as compared to the previous DR14 version, include the addition of molecular H2O and FeH lines, as well as a much larger (by a factor of ∼4) atomic line list, including a significantly greater number of transitions with hyperfine splitting. More recent references and line lists for the crucial molecules, CO and OH, as well as for C2 and SiH, are also included. In contrast to DR14, DR16 contains measurable lines from the heavy neutron-capture elements cerium (as Ce II), neodymium (as Nd II), and ytterbium (as Yb II), as well as one line from rubidium (as Rb I), which may be detectable in a small fraction of APOGEE red giants.

Keywords: High resolution spectroscopy, Atomic spectroscopy, Molecular spectroscopy, Spectroscopy
Efficient Detection of Emission-line Galaxies in the Cl0016+1609 and MACSJ1621.4+3810 Supercluster Filaments Using SITELLE. We observe a system of filaments and clusters around Cl0016+1609 and MACSJ1621.4+3810 using the SITELLE Fourier transform spectrograph at the Canada-France-Hawaii Telescope. For Cl0016+1609 (z = 0.546), the observations span an 11.8 Mpc × 4.3 Mpc region along an eastern filament that covers the main cluster core, as well as two 4.3 Mpc × 4.3 Mpc regions that each cover southern subclumps. For MACSJ1621.4+3810 (z = 0.465), 3.9 Mpc × 3.9 Mpc around the main cluster core is covered. We present the frequency and location of the emission-line galaxies and their emission-line images, and calculate the star formation rates, specific star formation rates, and merger statistics. In Cl0016+1609, we find 13 [O II] 3727 Å emitting galaxies with star formation rates between 0.2 and 14.0 M⊙ yr-1. Of these, ${91}_{-10}^{+3}$ % are found in regions with moderate local galaxy density, avoiding the dense cluster cores. These galaxies follow the main filament of the superstructure and are mostly blue and disky, with several showing close companions and merging morphologies. In MACSJ1621.4+3810, we find 10 emission-line sources. All are blue ( ${100}_{-15}^{+0}$ %), with ${40}_{-12}^{+16}$ % classified as disky and ${60}_{-16}^{+12}$ % as merging systems. Eight avoid the cluster core ( ${80}_{-17}^{+7}$ %), but two ( ${20}_{-7}^{+17}$ %) are found near high-density regions, including the brightest cluster galaxy (BCG). These observations push the spectroscopic study of galaxies in filaments beyond z ∼ 0.3 to z ∼ 0.5. Their efficient confirmation is paramount to their usefulness as more galaxy surveys come online. * Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated from the summit of Maunakea by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. The observations at the Canada-France-Hawaii Telescope were performed with care and respect from the summit of Maunakea which is a significant cultural and historic site. The corresponding proposals were: 17BF001, 18BF001 and 19AF001.

Keywords: Galaxy clusters, Galaxy colors, Superclusters, Emission line galaxies, Galaxy masses, Intergalactic filaments
Measuring Young Stars in Space and Time. I. The Photometric Catalog and Extinction Properties of N44. In order to better understand the role of high-mass stellar feedback in regulating star formation in giant molecular clouds, we carried out a Hubble Space Telescope (HST) Treasury Program Measuring Young Stars in Space and Time (MYSST) targeting the star-forming complex N44 in the Large Magellanic Cloud (LMC). Using the F555W and F814W broadband filters of both the ACS and WFC3/UVIS, we built a photometric catalog of 461,684 stars down to mF555W ≃ 29 mag and mF814W ≃ 28 mag, corresponding to the magnitude of an unreddened 1 Myr pre-main-sequence star of ≈ 0.09 M⊙ at the LMC distance. In this first paper we describe the observing strategy of MYSST and the data reduction procedure and present the photometric catalog. We identify multiple young stellar populations tracing the gaseous rim of N44's superbubble, together with various contaminants belonging to the LMC field population. We also determine the reddening properties from the slope of the elongated red clump (RC) feature by applying the machine-learning algorithm RANSAC, and we select a set of upper-main-sequence stars as primary probes to build an extinction map, deriving a relatively modest median extinction AF555W ≃ 0.77 mag. The same procedure applied to the RC provides AF555W ≃ 0.68 mag.

Keywords: Surveys, Star forming regions, Young star clusters, HST photometry, Large Magellanic Cloud, Pre-main sequence stars, Low mass stars
Measuring Young Stars in Space and Time. II. The Pre-main-sequence Stellar Content of N44. The Hubble Space Telescope survey Measuring Young Stars in Space and Time (MYSST) entails some of the deepest photometric observations of extragalactic star formation, capturing even the lowest-mass stars of the active star-forming complex N44 in the Large Magellanic Cloud. We employ the new MYSST stellar catalog to identify and characterize the content of young pre-main-sequence (PMS) stars across N44 and analyze the PMS clustering structure. To distinguish PMS stars from more evolved line of sight contaminants, a non-trivial task due to several effects that alter photometry, we utilize a machine-learning classification approach. This consists of training a support vector machine (SVM) and a random forest (RF) on a carefully selected subset of the MYSST data and categorize all observed stars as PMS or non-PMS. Combining SVM and RF predictions to retrieve the most robust set of PMS sources, we find ∼26,700 candidates with a PMS probability above 95% across N44. Employing a clustering approach based on a nearest neighbor surface density estimate, we identify 16 prominent PMS structures at 1σ significance above the mean density with sub-clusters persisting up to and beyond 3σ significance. The most active star-forming center, located at the western edge of N44's bubble, is a subcluster with an effective radius of ∼5.6 pc entailing more than 1100 PMS candidates. Furthermore, we confirm that almost all identified clusters coincide with known H II regions and are close to or harbor massive young O stars or YSOs previously discovered by MUSE and Spitzer observations.

Keywords: Star forming regions, Young star clusters, Large Magellanic Cloud, Pre-main sequence stars, Random Forests, Low mass stars, Support vector machine
Effect of Near-field Distribution on Transmission Characteristics of Fiber-fed Fabry-Perot Etalons. Fiber-fed etalons are widely employed in advanced interferometric instruments such as gravitational-wave detectors, ultrastable lasers and calibration reference for high-precision spectrographs. We demonstrate that variation in near-field distribution of the feeding fiber would deteriorate the spectrum precision of the fiber-fed Fabry-Perot etalon, especially when precision at the order of 3 × 10-10 or higher is required. The octagonal fiber reinforced with double scrambler could greatly improve the steadiness and uniformness of the near-field distribution. When building wavelength calibrators for sub-m s-1 precision radial-velocity instruments, the double scrambler should be considered meticulously.

Keywords: Fabry-Perot interferometers, Radial velocity, Spectral energy distribution
Time-domain Modulation of HD 189733 Activities by Its Planet. Star-planet interaction can be studied by analyzing exoplanetary orbit and stellar rotation modulations of the transit emissions from exoplanetary systems. Here we carry out a time-domain analysis of the multiband activities of the HD 189733 star-planet system observed in X-ray, atomic lines, and broadband spectra reported in the literature. We find that the number of activities occuring at beat angles (of the planetary orbit and the stellar rotation) concentrating on a sector with a width of 108° are significantly larger than expected from a uniform distribution of activities, which indicates the existence of a major stellar active magnetic field region. The concentration of activities in this active magnetic field region shows their possible origins from the magnetic field interaction between HD 189733 and its close planet HD 189733 b.

Keywords: Stellar flares, Exoplanets
On the Correlation between Atomic Gas and Bars in Galaxies. We analyze the correlation between properties of large-scale bars and atomic gas content of galaxies to explore the role of H I gas on bar evolution in galaxies. We show that the absolute bar size depends strongly on total stellar mass of galaxies and does not change significantly with H I gas fraction at fixed stellar mass. Furthermore, the physical size of the bar is small and nearly constant in high H I gas fraction and low-mass galaxies and becomes larger with increasing galactic stellar mass in low gas fraction galaxies. When the stellar masses are fixed, the relative bar length normalized to the disk shows a decrease with increasing H I gas fraction due to the larger disks in gas-richer galaxies. We measure the gas deficiency of the samples and find that the gas-rich galaxies have longer and stronger bars compared with the H I gas-deficient galaxies at fixed stellar mass, especially for the massive ones. When splitting the samples into star-forming and quiescent subgroups, the star-forming galaxies tend to have longer bars than the quiescent ones at fixed stellar mass and gas deficiency. In addition, our results suggest two different types of bar properties, in which the bars in gas-rich galaxies grow longer but retain similar axial ratio over time, while they grow longer and fatter over time in gas-poor galaxies.

Keywords: Barred spiral galaxies, Star formation, Galaxy evolution, Interstellar atomic gas
Systematics and Consequences of Comet Nucleus Outgassing Torques. Anisotropic outgassing from comets exerts a torque sufficient to rapidly change the angular momentum of the nucleus, potentially leading to rotational instability. Here, we use empirical measures of spin changes in a sample of comets to characterize the torques, and to compare them with expectations from a simple model. Both the data and the model show that the characteristic spin-up timescale, τs, is a strong function of nucleus radius, rn. Empirically, we find that the timescale for comets (most with perihelion 1-2 au and eccentricity ∼0.5) varies as ${\tau }_{s}\sim 100{r}_{{\rm{n}}}^{2}$ , where rn is expressed in kilometers, and τs is in years. The fraction of the nucleus surface that is active varies as ${f}_{{\rm{A}}}\sim 0.1{r}_{{\rm{n}}}^{-2}$ . We find that the median value of the dimensionless moment arm of the torque is kT = 0.007 (i.e., ∼0.7% of the escaping momentum torques the nucleus), with weak (&lt;3σ) evidence for a size dependence ${k}_{T}\sim {10}^{-3}{r}_{{\rm{n}}}^{2}$ . Sub-kilometer nuclei have spin-up timescales comparable to their orbital periods, confirming that outgassing torques are quickly capable of driving small nuclei toward rotational disruption. Torque-induced rotational instability likely accounts for the paucity of sub-kilometer short-period cometary nuclei, and for the pre-perihelion destruction of sungrazing comets. Torques from sustained outgassing on small active asteroids can rival YORP torques, even for very small (≲1 g s-1) mass-loss rates. Finally, we highlight the important role played by observational biases in the measured distributions of τs, fA, and kT.

Keywords: Comet nuclei, Short period comets, Near-sun comets