Sazuna/UAT_keywords huggingface dataset:
Scanning Disk Rings and Winds in CO at 0.01-10 au: A High-resolution M-band Spectroscopy Survey with IRTF-iSHELL. We present an overview and first results from a M-band spectroscopic survey of planet-forming disks performed with iSHELL on the Infrared Telescope Facility, using two slits that provide resolving power R ≍ 60,000-92,000 (5-3.3 km s-1). iSHELL provides a nearly complete coverage at 4.52-5.24 μm in one shot, covering &gt;50 lines from the R and P branches of 12CO and 13CO for each of multiple vibrational levels, and providing unprecedented information on the excitation of multiple emission and absorption components. Some of the most notable new findings of this survey are: (1) the detection of two CO Keplerian rings at &lt;2 au (in HD 259431), (2) the detection of H2O rovibrational lines at 5 μm (in AS 205 N), and (3) the common kinematic variability of CO lines over timescales of 1-14 yr. By homogeneously analyzing this survey together with a previous survey of cooler stars, we discuss a unified view of CO spectra where emission and absorption components scan the disk surface across radii from a dust-free region within dust sublimation out to ≍10 au. We classify two fundamental types of CO line shapes interpreted as emission from Keplerian rings (double-peak lines) and a disk surface plus a low-velocity part of a wind (triangular lines), where CO excitation reflects different emitting regions (and their gas-to-dust ratio) rather than just the irradiation spectrum. A disk+wind interpretation for the triangular lines naturally explains several properties observed in CO spectra, including the line blueshifts, line shapes that turn into narrow absorption at high inclinations, and the frequency of disk winds as a function of the stellar type.

Keywords: High resolution spectroscopy, Herbig Ae/Be stars, Molecular gas, Molecular spectroscopy, Classical T Tauri stars, Stellar winds, Pre-main sequence stars, Protoplanetary disks, Circumstellar disks, Exoplanet formation, Planet formation, Near infrared astronomy
TESS Revisits WASP-12: Updated Orbital Decay Rate and Constraints on Atmospheric Variability. After observing WASP-12 in the second year of the primary mission, the Transiting Exoplanet Survey Satellite (TESS) revisited the system in late 2021 during its extended mission. In this paper, we incorporate the new TESS photometry into a reanalysis of the transits, secondary eclipses, and phase curve. We also present a new K  s -band occultation observation of WASP-12b obtained with the Palomar/Wide-field Infrared Camera instrument. The latest TESS photometry spans three consecutive months, quadrupling the total length of the TESS WASP-12 light curve and extending the overall time baseline by almost two years. Based on the full set of available transit and occultation timings, we find that the orbital period is shrinking at a rate of -29.81 ± 0.94 ms yr-1. The additional data also increase the measurement precision of the transit depth, orbital parameters, and phase-curve amplitudes. We obtain a secondary eclipse depth of 466 ± 35 ppm, a 2σ upper limit on the nightside brightness of 70 ppm, and a marginal 6.°2 ± 2.°8 eastward offset between the dayside hotspot and the substellar point. The voluminous TESS data set allows us to assess the level of atmospheric variability on timescales of days, months, and years. We do not detect any statistically significant modulations in the secondary eclipse depth or day-night brightness contrast. Likewise, our measured K  s -band occultation depth of 2810 ± 390 ppm is consistent with most ~2.2 μm observations in the literature.

Keywords: Exoplanet astronomy, Transit photometry, Hot Jupiters
Prediction of Astrometric-microlensing Events from Gaia eDR3 Proper Motions. Astrometric microlensing is a unique tool to measure stellar masses. It allows us to determine the mass of the lensing star with an accuracy of a few percent. In this paper, we update, extend, and refine our predictions of astrometric-microlensing events based on Gaia's early Data release 3 (eDR3). We selected about 500.000 high-proper-motion stars from Gaia eDR3 with μ tot &gt; 100 mas yr-1 and searched for background sources close to their paths. We applied various selection criteria and cuts in order to exclude spurious sources and co-moving stars. By forecasting the future positions of lens and source, we determined epoch of and angular separation at closest approach, and determined an expected positional shift and magnification. Using Gaia eDR3, we predict 1758 new microlensing events with expected shifts larger than 0.1 mas between the epochs J2010.5 and mid J2066.0. Further, we provide more precise information on the angular separation at closest approach for 3084 previously predicted events. This helps to select better targets for observations, especially for events that occur within the next decade. Our search lead to the new prediction of an interesting astrometric-microlensing event by the white dwarf Gaia eDR3-4053455379420641152. In 2025 it will pass by a G = 20.25 mag star, which will lead to a positional shift of the major image of $\delta {\theta }_{+}={1.2}_{-0.5}^{+2.0}\,\mathrm{mas}$ . Since the background source is only ∆G = 2.45 mag fainter than the lens, also the shift of the combined center of light will be measurable, especially using a near-infrared filter, where the background star is brighter than the lens (∆Ks = -1.1 mag). *The results of the predicted microlensing events is available in electronic form via the GAVO Data Center https://dc.g-vo.org/amlensing/q3/q/form. †The source code for this study is made publicly available https://github.com/jkluter/amlensing.

Keywords: White dwarf stars, Astrometric microlensing effect, Astrometry, Proper motions, Stellar masses, Catalogs
Mass Transfer as an Explanation for the Lifetime Travel Time Discrepancy in IT Librae. The eclipsing binary IT Librae is an unusual system of two B-type stars that is situated about 1 kpc above the Galactic plane. The binary was probably ejected from its birthplace in the disk, but the implied time of flight to its current location exceeds the evolutionary lifetime of the primary star. Here we present a study of new high-dispersion spectroscopy and an exquisite light curve from the Kepler K2 mission in order to determine the system properties and resolve the timescale discrepancy. We derive a revised spectroscopic orbit from radial-velocity measurements and determine the component effective temperatures through comparison of reconstructed and model spectra (T 1 = 23.8 ± 1.8 kK, T 2 = 13.7 ± 2.5 kK). We use the Eclipsing Light Curve code to model the K2 light curve, and from the inclination of the fit we derive the component masses (M 1 = 9.6 ± 0.6 M ⊙, M 2 = 4.2 ± 0.2 M ⊙) and mean radii (R 1 = 6.06 ± 0.16 R ⊙, R 2 = 5.38 ± 0.14 R ⊙). The secondary star is overluminous for its mass and appears to fill its Roche lobe. This indicates that IT Librae is a post-mass-transfer system in which the current secondary was the mass donor star. The current primary star was rejuvenated by mass accretion, and its evolutionary age corresponds to the time since the mass transfer stage. Consequently, the true age of the binary is larger than the ejection time of flight, thus resolving the timescale discrepancy.

Keywords: Eclipsing binary stars, High latitude field, B stars, Binary stars
The Solar Neighborhood. XLIX. New Discoveries and Orbits of M-dwarf Multiples with Speckle Interferometry at SOAR. We present the first results of a multiyear program to map the orbits of M-dwarf multiples within 25 pc. The observations were conducted primarily during 2019-2020 using speckle interferometry at the Southern Astrophysical Research Telescope in Chile, using the High-Resolution Camera mounted on the adaptive optics module (HRCam+SAM). The sample of nearby M dwarfs is drawn from three sources: multiples from the RECONS long-term astrometric monitoring program at the SMARTS 0.9 m; known multiples, for which these new observations will enable or improve orbit fits; and candidate multiples flagged by their astrometric fits in Gaia Data Release 2 (DR2). We surveyed 333 of our 338 M dwarfs via 830 speckle observations, detecting companions for 63% of the stars. Most notably, this includes new companions for 76% of the subset selected from Gaia DR2. In all, we report the first direct detections of 97 new stellar companions to the observed M dwarfs. Here we present the properties of those detections, the limits of each nondetection, and five orbits with periods 0.67-29 yr already observed as part of this program. Companions detected have projected separations of 0.″024-2.″0 (0.25-66 au) from their primaries and have ΔI ≲ 5.0 mag. This multiyear campaign will ultimately map complete orbits for nearby M dwarfs with periods up to 3 yr, and provide key epochs to stretch orbital determinations for binaries to 30 yr.

Keywords: Binary stars, M stars, Astrometric binary stars, Astrometry, Low mass stars, Speckle interferometry
The California-Kepler Survey. X. The Radius Gap as a Function of Stellar Mass, Metallicity, and Age. In 2017, the California-Kepler Survey (CKS) published its first data release (DR1) of high-resolution optical spectra of 1305 planet hosts. Refined CKS planet radii revealed that small planets are bifurcated into two distinct populations, super-Earths (smaller than 1.5 R ⊕) and sub-Neptunes (between 2.0 and 4.0 R ⊕), with few planets in between (the "radius gap"). Several theoretical models of the radius gap predict variation with stellar mass, but testing these predictions is challenging with CKS DR1 due to its limited M ⋆ range of 0.8-1.4 M ☉. Here we present CKS DR2 with 411 additional spectra and derived properties focusing on stars of 0.5-0.8 M ☉. We found that the radius gap follows R  p  ∝ P  m  with m = -0.10 ± 0.03, consistent with predictions of X-ray and ultraviolet- and core-powered mass-loss mechanisms. We found no evidence that m varies with M ⋆. We observed a correlation between the average sub-Neptune size and M ⋆. Over 0.5-1.4 M ☉, the average sub-Neptune grows from 2.1 to 2.6 R ⊕, following ${R}_{p}\propto {M}_{\star }^{\alpha }$ with α = 0.25 ± 0.03. In contrast, there is no detectable change for super-Earths. These M ⋆-R  p  trends suggest that protoplanetary disks can efficiently produce cores up to a threshold mass of M  c , which grows linearly with stellar mass according to M  c  ≍ 10 M ⊕(M ⋆/M ☉). There is no significant correlation between sub-Neptune size and stellar metallicity (over -0.5 to +0.5 dex), suggesting a weak relationship between planet envelope opacity and stellar metallicity. Finally, there is no significant variation in sub-Neptune size with stellar age (over 1-10 Gyr), which suggests that the majority of envelope contraction concludes after ~1 Gyr.

Keywords: High resolution spectroscopy, Exoplanets, Super Earths, Exoplanet formation, Exoplanet astronomy, Mini Neptunes, Transit photometry
Nine Bright γ Doradus Variables Discovered with Ground-based Photometry. We have used precise photometric and high-dispersion spectroscopic observations to study nine candidate γ Doradus (γ Dor) stars, identified as optically variable comparison stars in our photometric studies of Sun-like stars. In this paper, we confirm these nine candidates as new γ Dor variables. All exhibit sinusoidal variability with amplitudes between 6 and 65 mmag in Johnson B and periods from 0.28 to 1.13 days. All lie in the same region of the H-R diagram as our previously confirmed γ Dor stars. Of the nine systems, one is a single-lined spectroscopic binary (SB1), two are double-lined spectroscopic binaries (SB2), and the remaining six are single stars. We present orbits for the three binary systems: HD 34415, HD 144839, and HD 182735. Their periods are 6400 days or 17.5 yr (adopted), 995 ± 7 days, and 1052.4 ± 0.2 days, respectively. We compare our photometric periods with those we derive for six of the nine stars observed with the Transiting Exoplanet Survey Satellite to strengthen the confirmation of these new γ Dor variables. Finally, because the distribution of γ Dor stars in the H-R diagram overlaps with the red edge of the δ Scuti (δ Sct) instability strip, we use our ground-based photometric results for the 73 γ Dor stars confirmed with our Automatic Photoelectric Telescopes over the past two decades to look at the incidence of hybrid δ Sct/γ Dor stars; these are highly valuable targets for asteroseismology.

Keywords: Stellar photometry, Early-type stars, Period determination, Stellar oscillations, Fundamental parameters of stars, Spectroscopic binary stars, Radial velocity, Gamma Doradus variable stars
Reassessing the Evidence for Time Variability in the Atmosphere of the Exoplanet HAT-P-7 b<SUB>f</SUB>. We reassess the claimed detection of variability in the atmosphere of the hot Jupiter HAT-P-7 b, reported by Armstrong et al. Although astronomers expect hot Jupiters to have changing atmospheres, variability is challenging to detect. We looked for time variation in the phase curves of HAT-P-7 b in Kepler data using similar methods to Armstrong et al., and identified apparently significant variations similar to what they found. Numerous tests show the variations to be mostly robust to different analysis strategies. However, when we injected unchanging phase-curve signals into the light curves of other stars and searched for variability, we often saw similar levels of variations as in the HAT-P-7 light curve. Fourier analysis of the HAT-P-7 light curve revealed background red noise from stellar supergranulation on timescales similar to the planet's orbital period. Tests of simulated light curves with the same level of noise as HAT-P-7's supergranulation show that this effect alone can cause the amplitude and phase-offset variability we detect for HAT-P-7 b. Therefore, the apparent variations in HAT-P-7 b's atmosphere could instead be caused by nonplanetary sources, most likely photometric variability due to supergranulation on the host star.

Keywords: Exoplanet astronomy, Exoplanet atmospheric variability, Exoplanet atmospheres
Atmospheric and Fundamental Parameters of Eight Nearby Multiple Stars. We present the complete set of atmospheric and fundamental parameters, in addition to the masses, for the individual components of eight stellar systems. The list of the systems, whose orbital solutions were published recently, includes seven binaries (HIP 14524, HIP 16025, HIP 46199, HIP 47791, HIP 60444, HIP 61100, HIP 73085) and one triple system (HIP 28671). The systems were analyzed using a spectrophotometric computational technique known as Al-Wardats method for analyzing binary and multiple stellar systems, which makes use of ATLAS9 line-blanketed plane-parallel model atmospheres. Using these estimated parameters, the positions of the components were located on the Hertzsprung-Russell diagram, evolutionary tracks and isochrones to estimate their ages, the range depending on the uncertainties in their metallicities. Five systems were found to be pre-main-sequence stars (HIP 14524, HIP 46199, HIP 60444, HIP 61100, HIP 73085), two were main-sequence stars (the zero-age HIP 28671 and the 6.3 Gyr HIP 16025), and one is a subgiant system (HIP 47791) with an age of 1.4 Gyr. Fragmentation is proposed as the most probable formation process for the eight systems. A comparison between the estimated masses and the dynamical ones lead to new dynamical parallaxes for four systems: (28.63 ± 0.56) mas for HIP 14524, (15.6 ± 0.63) mas for HIP 16025, (9.73 ± 0.26) mas for HIP 47791, and (16.53 ± 0.59) mas for HIP 73085. Hence, the orbital solutions were reclassified. We conclude that Gaia DR3 parallaxes are more precise than those given by Gaia DR2 and Hipparcos 2.

Keywords: Multiple stars, Binary stars, Multiple star evolution
Five Decades of Chromospheric Activity in 59 Sun-like Stars and New Maunder Minimum Candidate HD 166620. We present five decades of chromospheric activity measurements in 59 Sun-like stars as time series. These include and extend the 35 yr of stellar chromospheric activity observations by the Mount Wilson Survey (1966-2001), and continued observations at Keck by the California Planet Search (1996-). The Mount Wilson Survey was studied closely in 1995, and revealed periodic activity cycles similar to the Sun's 11 yr cycle. The California Planet Search provides more than five decades of measurements, significantly improving our understanding of these stars' activity behavior. We have curated the activity measurements in order to create contiguous time series, and have classified the stellar sample according to a predetermined system. We have analyzed 29 stars with periodic cycles using the Lomb-Scargle periodogram, and present best-fit sinusoids to their activity time series. We report the best-fit periods for each cycling star, along with stellar parameters (T eff, log(g), vsin(i), etc.) for the entire sample. As a first application of these data, we offer a possible Maunder minimum candidate, HD 166620.

Keywords: Solar cycle, Stellar chromospheres, Stellar activity, Maunder minimum, Magnetic fields
Observing the Sun as a Star: Design and Early Results from the NEID Solar Feed. Efforts with extreme-precision radial velocity (EPRV) instruments to detect small-amplitude planets are largely limited, on many timescales, by the effects of stellar variability and instrumental systematics. One avenue for investigating these effects is the use of small solar telescopes which direct disk-integrated sunlight to these EPRV instruments, observing the Sun at high cadence over months or years. We have designed and built a solar feed system to carry out "Sun-as-a-star" observations with NEID, a very high precision Doppler spectrometer recently commissioned at the WIYN 3.5 m Telescope at Kitt Peak National Observatory. The NEID solar feed has been taking observations nearly every day since 2020 December; data is publicly available at the NASA Exoplanet Science Institute NEID Solar Archive: https://neid.ipac.caltech.edu/search_solar.php. In this paper, we present the design of the NEID solar feed and explanations behind our design intent. We also present early radial velocity (RV) results which demonstrate NEID's RV stability on the Sun over 4 months of commissioning: 0.66 m s-1 rms under good sky conditions and improving to 0.41 m s-1 rms under best conditions.

Keywords: Solar activity, Radial velocity, Exoplanets, Solar telescopes
Validation and Improvement of the Pan-STARRS Photometric Calibration with the Stellar Color Regression Method. As one of the best ground-based photometric data set, Pan-STARRS1 (PS1) has been widely used as the reference to calibrate other surveys. In this work, we present an independent validation and recalibration of the PS1 photometry using spectroscopic data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) DR7, and photometric data from the corrected Gaia Early Data Release 3 (EDR3) with the Stellar Color Regression (SCR) method. Using per band typically a total of 1.5 million LAMOST-PS1-Gaia stars as standards, we show that the PS1 photometric calibration precisions in the grizy filters are around 4 ~ 5 mmag when averaged over 20' regions. However, significant large- and small-scale spatial variation of magnitude offset, up to over 1%, probably caused by the calibration errors in the PS1, are found for all the grizy filters. The calibration errors in different filters are uncorrelated, and are slightly larger for the g and y filters. We also detect moderate magnitude-dependent errors (0.005, 0.005, 0.005, 0.004, 0.003 mag per magnitude in the 14-17 mag range for the grizy filters, respectively) in the PS1 photometry by comparing with the Gaia EDR3 and other catalogs. The errors are likely caused by the systematic uncertainties in the PSF magnitudes. We provide two-dimensional maps to correct for such magnitude offsets in the LAMOST footprint at different spatial resolutions from 20' to 160'. The results demonstrate the power of the SCR method in improving the calibration precision of wide-field surveys when combined with the LAMOST spectroscopy and Gaia photometry.

Keywords: Stellar photometry, Calibration, Astronomy data analysis
An Automatic Identification Method for the Photoelectron Boundary at Mars. The photoelectron boundary (PEB) at Mars is defined to be the boundary separating the photoelectron-dominated ionosphere from the external plasma environment. Extensive studies have been presented to analyze the PEB variation in the Martian dayside ionosphere. However, the PEB was identified manually in previous studies because of the difficulty in detecting the faint photoelectron features at high altitudes. In this study, we develop an algorithm to detect these faint features and identify the location of PEB from energetic electron measurements automatically. We apply the algorithm to the measurements by the Solar Wind Electron Analyzer instrument on board the Mars Atmosphere and Volatile Evolution mission and identify a total number of 15,681 PEB crossing events accumulated from 2015 January to 2019 October, of which 9169 PEB are on the dayside and 6912 are on the nightside. Our analysis indicates that the altitude of the identified PEB tends to increase with solar extreme ultraviolet radiation and crustal magnetic field strength, in agreement with previous findings. By contrast, the PEB altitude on the nightside tends to increase dramatically with solar zenith angle but is found to be weakly influenced by the crustal magnetic field strength.

Keywords: Mars, Planetary ionospheres
Optimal Differential Astrometry for Multiconjugate Adaptive Optics. I. Astrometric Distortion Mapping using On-sky GeMS Observations of NGC 6723. The Extremely Large Telescope and the Thirty Meter Telescope will use state of the art multiconjugate adaptive optics (MCAO) systems to obtain the full D 4 advantage that their apertures can provide. However, to reach the full astrometric potential of these facilities for on-sky science requires understanding any residual astrometric distortions from these systems and find ways to measure and eliminate them. In this work, we use Gemini multiconjugate adaptive optic system (GeMS) observations of the core of NGC 6723 to better understand the on-sky astrometric performance of MCAO. We develop new methods to measure the astrometric distortion fields of the observing system, which probe the distortion at the highest possible spatial resolution. We also describe methods for examining the time-variable and static components of the astrometric distortion. When applied to the GeMS Gemini South Adaptive Optics Imager (GSAOI) data, we are able to see the effect of the field rotator at the subpixel level, and we are able to empirically derive the distortion due to the optical design of GeMS/GSAOI. We argue that the resulting distortion maps are a valuable tool to measure and monitor the on-sky astrometric performance of future instrumentation. Our overall astrometry pipeline produces high-quality proper motions with an uncertainty floor of ~45 μas yr-1. We measure the proper motion dispersion profile of NGC 6723 from a radius of ~10″ out to ~1' based on ~12,000 stars. We also produce a high-quality optical-near infrared color-magnitude diagram, which clearly shows the extreme horizontal branch and main-sequence knee of this cluster.

Keywords: Globular star clusters, Astronomical optics, Astronomical instrumentation, Astrometry, Proper motions, Astronomical seeing, Ground telescopes