Sazuna/UAT_keywords huggingface dataset:
Two Luminous Post-AGB Stars in the Galactic Globular Cluster M19. We report the discovery of a luminous "yellow" post-asymptotic giant branch (PAGB) star in the globular cluster (GC) M19 (NGC 6273), identified during our uBVI survey of Galactic GCs. The uBVI photometric system is optimized to detect stars with large Balmer discontinuities, indicating very low surface gravities and high luminosities. The spectral energy distribution (SED) of the star is consistent with an effective temperature of about 6250 K and a surface gravity of $\mathrm{log}g=0.5$ . We use Gaia data to show that the star's proper motion and radial velocity are consistent with cluster membership. One aim of our program is to test yellow PAGB stars as candidate Population II standard candles for determining extragalactic distances. We derive a visual absolute magnitude of MV = - 3.39 ± 0.09 for the M19 star. This is in close agreement with the MV values found for yellow PAGB stars in the GCs ω Cen, NGC 5986, and M79, indicating a very narrow luminosity function. These objects are 4 mag brighter than RR Lyrae variables, and they can largely avoid the issues of interstellar extinction that are a problem for Population I distance indicators. We also identified a second luminous PAGB object in M19, this one a hotter "UV-bright" star. Its SED is consistent with an effective temperature of about 11,750 K and $\mathrm{log}g=2.0$ . The two objects have nearly identical bolometric luminosities, $\mathrm{log}L/{L}_{\odot }=3.24$ and 3.22, respectively.

Keywords: Globular star clusters, Post-asymptotic giant branch stars, Late stellar evolution
KMT-2017-BLG-2820 and the Nature of the Free-floating Planet Population. We report a new free-floating planet (FFP) candidate, KMT-2017-BLG-2820, with Einstein radius θE ≃ 6 μas, lens-source relative proper motion μrel ≃ 8 mas yr-1, and Einstein timescale tE = 6.5 hr. It is the third FFP candidate found in an ongoing study of giant-source finite-source point-lens (FSPL) events in the KMTNet database and the sixth FSPL FFP candidate overall. We find no significant evidence for a host. Based on their timescale distributions and detection rates, we argue that five of these six FSPL FFP candidates are drawn from the same population as the six point-source point-lens (PSPL) FFP candidates found by Mróz et al. in the OGLE-IV database. The θE distribution of the FSPL FFPs implies that they are either sub-Jovian planets in the bulge or super-Earths in the disk. However, the apparent "Einstein desert" (10 ≲ θE/μas ≲ 30) would argue for the latter. Whether each of the 12 (six FSPL and six PSPL) FFP candidates is truly an FFP or simply a very wide-separation planet can be determined at first adaptive optics (AO) light on 30 m telescopes, and earlier for some. If the latter, a second epoch of AO observations could measure the projected planet-host separation with a precision of ${ \mathcal O }(10\,\mathrm{au})$ . At the present time, the balance of evidence favors the unbound-planet hypothesis.

Keywords: Gravitational microlensing
Diffuse Bands 9577 and 9633: Relations to Other Interstellar Features. We study, for the first time, the relations of two strong diffuse bands (DIBs) at 9633 and 9577 Å, commonly attributed to   ${{\rm{C}}}_{60}^{+}$  &lt;!--    C   60   +    --&gt; , to other interstellar features seen in optical and UV spectra including H I, Ca I, Fe II, Na I, Ti II, CN, CH, CH+, and C2 and DIBs 5780, 5797, 6196, 6269, 6284, and 6614. We analyzed 62 lines of sight where the stellar contamination by Mg II was corrected or found negligible for DIB 9633. Equivalent widths of DIB 9577 were measured in 62 lines of sight. Poor mutual correlation between the strengths of the above features and the major diffuse bands (5780 and 5797) as well as with other DIBs (with some exceptions) were revealed. The considered DIBs are also poorly correlated with the features of neutral hydrogen, molecular carbon, and those of simple interstellar radicals. Perhaps this phenomenon can be explained if the diffuse band 9577 is an unresolved blend of two or more interstellar features. There are indications that 9633 and 9577 diffuse bands are stronger in σ-type clouds, i.e., these features resemble the behavior of reasonably broad DIBs, which are strong in the lines of sight where the UV flux from the very hot nearby stars plays an important role.

Keywords: Interstellar line absorption, Diffuse interstellar bands, Interstellar medium, Interstellar absorption
Chemical Compositions of Red Giant Stars from Habitable Zone Planet Finder Spectroscopy. We have used the Habitable Zone Planet Finder (HPF) to gather high-resolution, high signal-to-noise near-infrared spectra of 13 field red horizontal branch (RHB) stars, one open cluster giant, and one very metal-poor halo red giant. The HPF spectra cover the 0.81-1.28 μm wavelength range of the zyJ bands, partially filling the gap between the optical (0.4-1.0 μm) and infrared (1.5-2.4 μm) spectra already available for the program stars. We derive abundances of 17 species from LTE-based computations involving equivalent widths and spectrum syntheses, and estimate abundance corrections for the species that are most affected by departures from LTE in RHB stars. Generally good agreement is found between HPF-based metallicities and abundance ratios and those from the optical and infrared spectral regions. Light element transitions dominate the HPF spectra of these red giants, and HPF data can be used to derive abundances from species with poor or no representation in optical spectra (e.g., C I, P I, S I, K I). Attention is drawn to the HPF abundances in two field solar-metallicity RHB stars of special interest: one with an extreme carbon isotope ratio, and one with a rare, very large lithium content. The latter star is unique in our sample in exhibiting very strong He I 10830 Å absorption. The abundances of the open cluster giant concur with those derived from other wavelength regions. Detections of C I and S I in HD 122563 are reported, yielding the lowest metallicity determination of [S/Fe] from more than one multiplet.

Keywords: Horizontal branch, Chemical abundances, Atomic spectroscopy, Metallicity, Near infrared astronomy
Tidally Excited Modes and δ Scuti Pulsations in the Eclipsing Triple Star IM Persei. IM Per is a triple star system whose eclipsing pair masses and radii are accurate to within 1%. The Transiting Exoplanet Survey Satellite (TESS) light curve of the program target exhibits partial eclipses and multiple oscillations with millimagnitude-level amplitudes. It is found that the oscillations affect eclipse timing measurements. Binary modeling of the high-quality TESS data indicates that the eclipsing components of the triple system are twin dwarfs with parameters of M2/M1 = 0.995, R2/R1 = 0.901, and Δ( ${T}_{\mathrm{eff},1}$ - ${T}_{\mathrm{eff},2}$ ) = 12 K in an eccentric (e = 0.049), detached configuration. The third light of l3 = 0.054 may mostly come from a G-type tertiary companion. Our predicted parallax of 1.52 ± 0.09 mas is concurrent with the Gaia measurement of 1.52 ± 0.05 mas. Multifrequency analysis of the outside-eclipse residuals reveals 22 significant pulsation signals: 4 in the gravity-mode region (0.03-2.22 day-1) and 18 in the pressure-mode region (9.19-25.12 day-1). Of the low frequencies, f11 and f14 are orbital harmonics that can be identified as tidally excited modes. The pulsation periods and constants for the high frequencies, and the position in the Cepheid instability strip demonstrate that the pulsating component of IM Per is a δ Sct variable.

Keywords: Delta Scuti variable stars, Fundamental parameters of stars, Multi-periodic pulsation, Eclipsing binary stars, Stellar oscillations, Asteroseismology
Target Prioritization and Observing Strategies for the NEID Earth Twin Survey. NEID is a high-resolution optical spectrograph on the WIYN 3.5 m telescope at Kitt Peak National Observatory and will soon join the new generation of extreme precision radial velocity instruments in operation around the world. We plan to use the instrument to conduct the NEID Earth Twin Survey (NETS) over the course of the next 5 years, collecting hundreds of observations of some of the nearest and brightest stars in an effort to probe the regime of Earth-mass exoplanets. Even if we take advantage of the extreme instrumental precision conferred by NEID, it will be difficult to disentangle the weak (∼10 cm s-1) signals induced by such low-mass, long-period exoplanets from stellar noise for all but the quietest host stars. In this work, we present a set of quantitative selection metrics which we use to identify an initial NETS target list consisting of stars conducive to the detection of exoplanets in the regime of interest. We also outline a set of observing strategies with which we aim to mitigate uncertainty contributions from intrinsic stellar variability and other sources of noise.

Keywords: Exoplanet detection methods, Stellar properties, Exoplanets, Surveys, Radial velocity
TESS Observations of the WASP-121 b Phase Curve. We study the red-optical photometry of the ultrahot Jupiter WASP-121 b as observed by the Transiting Exoplanet Survey Satellite (TESS) and model its atmosphere through a radiative transfer simulation. Given its short orbital period of ∼1.275 days, inflated state, and bright host star, WASP-121 b is exceptionally favorable for detailed atmospheric characterization. Toward this purpose, we use allesfitter to characterize its full red-optical phase curve, including the planetary phase modulation and secondary eclipse. We measure the day- and nightside brightness temperatures in the TESS passband as ${3012}_{-42}^{+40}$ and ${2022}_{-602}^{+254}$ K, respectively, and do not find a statistically significant phase shift between the brightest and substellar points. This is consistent with inefficient heat recirculation on the planet. We then perform an atmospheric retrieval analysis to infer the dayside atmospheric properties of WASP-121 b, such as its bulk composition, albedo, and heat recirculation. We confirm the temperature inversion in the atmosphere and suggest H-, TiO, and VO as potential causes of the inversion, absorbing heat at optical wavelengths at low pressures. Future Hubble Space Telescope and James Webb Space Telescope observations of WASP-121 b will benefit from its first full phase curve measured by TESS.

Keywords: Exoplanet atmospheric composition , Hot Jupiters, Exoplanet astronomy, Extrasolar gaseous giant planets, Exoplanet atmospheres
Classifying High-cadence Microlensing Light Curves. I. Defining Features. Microlensing is a powerful tool for discovering cold exoplanets, and the Roman Space Telescope microlensing survey will discover over 1000 such planets. Rapid, automated classification of Roman's microlensing events can be used to prioritize follow-up observations of the most interesting events. Machine learning is now often used for classification problems in astronomy, but the success of such algorithms can rely on the definition of appropriate features that capture essential elements of the observations that can map to parameters of interest. In this paper, we introduce tools that we have developed to capture features in simulated Roman light curves of different types of microlensing events, and we evaluate their effectiveness in classifying microlensing light curves. These features are quantified as parameters that can be used to decide the likelihood that a given light curve is due to a specific type of microlensing event. This method leaves us with a list of parameters that describe features like the smoothness of the peak, symmetry, the number of peaks, and the width and height of small deviations from the main peak. This will allow us to quickly analyze a set of microlensing light curves and later use the resulting parameters as input to machine learning algorithms to classify the events.

Keywords: Gravitational microlensing, Light curve classification , Surveys
Searching for Active Low-mass Stars in the CMa Star-forming Region: Multi-band Photometry with T80S. An exotic environment surrounds the young stellar groups associated with the Canis Major (CMa) OB1/R1 region, which probably was formed under feedback from at least three supernova events having occurred a few million years ago. We use astrometric data from the Gaia-DR2 to confirm the membership of the stars in CMa R1, based on proper motion and parallax, which revealed 514 new members and candidates. The mean age of 5 Myr estimated from the color-magnitude diagram characterizes the sources as likely pre-main-sequence candidates. In total, a sample of 694 stars detected with the T80-South telescope was analyzed according to different color-color diagrams, which were compared with theoretical colors from evolutionary models, aiming to reveal the objects that exhibit color excess due to accretion processes. Accretion and magnetic activity were also explored on the basis of empirical flux-flux relation, such as F660 and F861 that are related to Hα and Ca II triplet emission, respectively. A low fraction (∼3 percent) of the sample have Hα excess and other colors expected for stars exhibiting chromospheric activity. The number of Class I and Class II objects, identified by the infrared (Wide-field Infrared Survey Explorer) colors, indicates a disk fraction of ∼6 percent, which is lower than that expected for stellar clusters with a similar age. Such a large sample of objects associated with CMa R1 without evidences of circumstellar accretion can be interpreted as a lack of disk-bearing stars, unusual for young star-forming regions. However, this may be explained as the result of supernova events.

Keywords: Star forming regions, Pre-main sequence stars, Young star clusters
Understanding the Impacts of Stellar Companions on Planet Formation and Evolution: A Survey of Stellar and Planetary Companions within 25 pc. We explore the impact of outer stellar companions on the occurrence rate of giant planets detected with radial velocities. We searched for stellar and planetary companions to a volume-limited sample of solar-type stars within 25 pc. Using adaptive optics imaging observations from the Lick 3 m and Palomar 200″ Telescopes, we characterized the multiplicity of our sample stars, down to the bottom of the main sequence. With these data, we confirm field star multiplicity statistics from previous surveys. We additionally combined three decades of radial velocity (RV) data from the California Planet Search with newly collected RV data from Keck/HIRES and the Automated Planet Finder/Levy Spectrometer to search for planetary companions in these same systems. Using an updated catalog of both stellar and planetary companions, as well as detailed injection/recovery tests to determine our sensitivity and completeness, we measured the occurrence rate of planets among the single- and multiple-star systems. We found that planets with masses in the range of 0.1-10 MJ and with semimajor axes of 0.1-10 au have an occurrence rate of ${0.18}_{-0.03}^{+0.04}$ planets per star when they orbit single stars and an occurrence rate of 0.12 ± 0.04 planets per star when they orbit a star in a binary system. Breaking the sample down by the binary separation, we found that only one planet-hosting binary system had a binary separation &lt;100 au, and none had a separation &lt;50 au. These numbers yielded planet occurrence rates of ${0.20}_{-0.06}^{+0.07}$ planets per star for binaries with separation aB &gt; 100 au and ${0.04}_{-0.02}^{+0.04}$ planets per star for binaries with separation aB &lt; 100 au. The similarity in the planet occurrence rate around single stars and wide primaries implies that wide binary systems should actually host more planets than single-star systems, since they have more potential host stars. We estimated a system-wide planet occurrence rate of 0.3 planets per wide binary system for binaries with separations aB &gt; 100 au. Finally, we found evidence that giant planets in binary systems have a different semimajor-axis distribution than their counterparts in single-star systems. The planets in the single-star sample had a significantly higher occurrence rate outside of 1 au than inside 1 au by nearly 4σ, in line with expectations that giant planets are most common near the snow line. However, the planets in the wide binary systems did not follow this distribution, but rather had equivalent occurrence rates interior and exterior to 1 au. This may point to binary-mediated planet migration acting on our sample, even in binaries wider than 100 au.

Keywords: Radial velocity, Exoplanet formation, Exoplanet catalogs, Planet hosting stars
Detectability of Optical Transients with Timescales of Subseconds. We search for optical transient sources with durations of ∼0.1 to ∼1.3 s using a data set obtained in the Organized Autotelescopes for Serendipitous Event Survey (OASES) observation campaign. Since the OASES observations were carried out using two independent wide-field and high-cadence observation systems monitored the same field simultaneously, the obtained data set provides a unique opportunity to develop a robust detection method for subsecond optical transients. In the data set of a selected field around the ecliptic and the Galactic plane, we find no astronomical event candidate that satisfies our detection criteria. From the nondetection result, we derive an upper limit on the event rate of subsecond transients around the ecliptic and the Galactic plane for the first time, obtaining ∼0.090 and ∼0.38 hr-1 deg-2 for m = 12 and 13 Vmag, respectively. In addition, future prospects of the subsecond-scale transient event surveys are discussed.

Keywords: Astronomical methods, Transient sources, Time domain astronomy
A Multiwavelength Look at the GJ 9827 System: No Evidence of Extended Atmospheres in GJ 9827b and d from HST and CARMENES Data. GJ 9827 is a bright star hosting a planetary system with three transiting planets. As a multiplanet system with planets that sprawl within the boundaries of the radius gap between terrestrial and gaseous planets, GJ 9827 is an optimal target to study the evolution of the atmospheres of close-in planets with a common evolutionary history and their dependence from stellar irradiation. Here we report on the Hubble Space Telescope (HST) and CARMENES transit observations of GJ 9827 planets b and d. We performed a stellar and ISM characterization from the ultraviolet HST spectra, obtaining fluxes for Lyα and Mg II of F(Lyα) = (5.42 ${}_{-0.75}^{+0.96}$ ) × 10-13 erg cm-2 s-1 and F(MgII) = (5.64 ± 0.24) × 10-14 erg cm-2 s-1. We also investigated a possible absorption signature in Lyα in the atmosphere of GJ 9827b during a transit event from HST spectra, as well as Hα and He I signature for the atmosphere of GJ 9827b and d from CARMENES spectra. We found no evidence of an extended atmosphere in either of the planets. This result is also supported by our analytical estimations of mass loss based on the measured radiation fields for all three planets of this system, which led to a mass-loss rate of 0.4, 0.3, and 0.1 planetary masses per Gyr for GJ 9827b, c, and d, respectively. These values indicate that the planets could have lost their volatiles quickly in their evolution and probably do not retain an atmosphere at the current stage.

Keywords: Exoplanet astronomy, Stellar chromospheres, Exoplanet atmospheres, Ultraviolet sources
The Pre-He White Dwarfs in Eclipsing Binaries. II. WASP 0843-11. We present the Transiting Exoplanet Survey Satellite (TESS) photometry and our high-resolution spectra of the EL CVn-type star 1SWASP J084356.46-113327.5 (WASP 0843-11), which consists of an F-type main-sequence (MS) star and a hotter low-mass helium white dwarf precursor (pre-He WD). In a spectral analysis, double-lined radial velocities (RVs) were obtained for the first time. From a simultaneous analysis of the TESS light and RV curves, the masses, radii, and temperatures of each component were determined to be M1 = 1.733 ± 0.031 M⊙, M2 = 0.220 ± 0.008 M⊙, R1 = 2.094 ± 0.013 R⊙, R2 = 0.331 ± 0.003 R⊙, T1 = 6960 ± 120 K, and T2 =9870 ± 310 K, respectively. According to their physical properties, the primary and secondary stars are located on the instability strips of δ Sct/γ Dor hybrids and extremely low-mass WDs, respectively. We applied multiple frequency analyses to the residual light curve after subtracting the binarity effects and detected a total of four independent frequencies. A frequency of f3 = 1.6356 day-1 in the low-frequency region was reminiscent of γ Dor stars, while the other three frequencies of f2, f15, and f18 in the high-frequency region (150-196 day-1) are probably related to pre-He WD components. Our results demonstrate that the more massive MS primary star of WASP 0843-11 is a γ Dor pulsator, whereas the hotter secondary component is a pre-He WD with high-frequency pulsations.

Keywords: Fundamental parameters of stars, White dwarf stars, Multi-periodic pulsation, Spectroscopy, Eclipsing binary stars, Stellar oscillations, Asteroseismology, Stellar evolution
The Initial Mass Function of Low-mass Stars and Brown Dwarfs in the W3 Complex. We have used archival infrared images obtained with the Wide Field Camera 3 on board the Hubble Space Telescope to constrain the initial mass function of low-mass stars and brown dwarfs in the W3 star-forming region. The images cover 438 arcmin2, which encompasses the entire complex, and were taken in the filters F110W, F139M, and F160W. We have estimated extinctions for individual sources in these data from their colors and have dereddened their photometry accordingly. By comparing an area of the images that contains the richest concentration of previously identified W3 members to an area that has few members and is dominated by background stars, we have estimated the luminosity function for members of W3 with masses of 0.03-0.4 M☉. That luminosity function closely resembles data in typical nearby star-forming regions that have much smaller stellar populations than W3 ( ≲ 500 versus several thousand objects). Thus, we do not find evidence of significant variations in the initial mass function of low-mass stars and brown dwarfs with star-forming conditions, which is consistent with recent studies of other distant massive star-forming regions.

Keywords: Hubble Space Telescope, Star forming regions, Brown dwarfs, Initial mass function
Low-metallicity Young Clusters in the Outer Galaxy. III. Sh 2-127. In deep near-infrared imaging of the low-metallicity ([O/H] = -0.7 dex) H II region Sh 2-127 (S127) with Subaru/MOIRCS, we detected two young clusters with 413 members (S127A) in a slightly extended H II region and another with 338 members (S127B) in a compact H II region. The limiting magnitude was K = 21.3 mag (10σ), corresponding to a mass detection limit of ∼0.2 ${M}_{\odot }$ . These clusters are an order of magnitude larger than previously studied young low-metallicity clusters and larger than the majority of solar neighborhood young clusters. Fits to the K-band luminosity functions indicate very young cluster ages of 0.5 Myr for S127A and 0.1-0.5 Myr for S127B, consistent with the large extinction (up to AV ≃ 20 mag) from thick molecular clouds and the presence of a compact H II region and class I source candidates, and suggest that the initial mass function (IMF) of the low-metallicity clusters is indistinguishable from typical solar neighborhood IMFs. Disk fractions of 28% ± 3% for S127A and 40% ± 4% for S127B are significantly lower than those of similarly aged solar neighborhood clusters (∼50%-60%). The disk fraction for S127B is higher than those of previously studied low-metallicity clusters (&lt;30%), probably due to S127B's age. This suggests that a large fraction of very young stars in low-metallicity environments have disks, but the disks are lost on a very short timescale. These results are consistent with our previous studies of low-metallicity star-forming regions, suggesting that a solar neighborhood IMF and low disk fraction are typical characteristics for low-metallicity regions, regardless of cluster scales.

Keywords: Galaxy abundances, Star formation, Protoplanetary disks, Infrared sources, Pre-main sequence, H II regions, Open star clusters, Metallicity