Sazuna/UAT_keywords huggingface dataset:
The η Aquilae System: Radial Velocities and Astrometry in Search of η Aql B. The classical Cepheid η Aql was not included in past Leavitt Law work because of a presumed complicating orbit due to a known B9.8V companion. To determine the orbit of η Aql B, we analyze a significant number of radial velocity (RV) measurements from eight sources. With these we establish the RV variation due to Cepheid pulsation, using a model with 12 Fourier coefficients, while solving for velocity offsets required to bring the RV data sets into coincidence. RV residuals provide no evidence of orbital motion, suggesting either nearly face-on orientation or a very long period. Reanalysis of Hubble Space Telescope Fine Guidance Sensor astrometry now includes reference star parallax and proper motion priors from Gaia EDR3. As modeling confirmation, we reanalyze ζ Gem in parallel, deriving values for its parallax and proper motion consistent with Gaia EDR3, and consistent with the Benedict 2007 Leavitt Law. In an effort to further characterize η Aql B, we hypothesize that η Aql residuals larger than those of the associated reference stars or a parallax inconsistent with EDR3 and the Benedict 2007 Leavitt Law indicate unmodeled orbital motion. Using the astrometric noise or parallax mismatch with EDR3, we estimate possible periods and mass for η Aql B. Ascribing photocenter motion to the photometric variation of the Cepheid, η Aql A, yields a plausible separation that is consistent with a long period and explains the lack of RV variation. None of these approaches yields an unassailable characterization of the η Aql A-B system.

Keywords: Cepheid variable stars, Young disk Cepheid variable stars
GPS Measurements of Precipitable Water Vapor Can Improve Survey Calibration: A Demonstration from KPNO and the Mayall z-band Legacy Survey. Dual-band Global Positioning Satellite (GPS) measurements of precipitable water vapor (PWV) at the Kitt Peak National Observatory predict the overall per-image sensitivity of the Mayall z-band Legacy Survey (MzLS). The per-image variation in the brightness of individual stars is strongly correlated with the measured PWV and the color of the star. Synthetic stellar spectra through TAPAS transmission models successfully predict the observed PWV-induced photometric variation. We find that PWV absorption can be well approximated by a linear relationship with (airmass × PWV)0.6 and present an update on the traditional treatment in the literature. The MzLS zero-point sensitivity in electrons s-1 varies with a normalized-mean absolute deviation of 61 mmag. PWV variation accounts 23 mmag of this zero-point variation. The MzLS per-image absolute sensitivity decreases by 40 mmag per effective mm of PWV. The overall gray offset portion of this variation is corrected by the calibration to a reference catalog. But the relative calibration error between blue (r - z &lt; 0.5 mag) versus red (1.2 mag &lt; r - z) stars increases by 0.3-2 mmag per effective mm of PWV. We argue that GPS systems provide more precise PWV measurements than using differential measurements of stars of different colors and recommend that observatories install dual-band GPS as a low-maintenance, low-cost, auxiliary calibration system. We extend our results of the need for well-calibrated PWV measurements by presenting the calculations of the PWV photometric impact on three science cases of interest: stellar photometry, supernova cosmology, and quasar identification and variability.

Keywords: Sky surveys, Water vapor, Earth atmosphere, Quasars, Observational cosmology, Flux calibration, Type Ia supernovae, Exoplanet detection methods, Astronomical methods
The unpopular Package: A Data-driven Approach to Detrending TESS Full-frame Image Light Curves. The majority of observed pixels on the Transiting Exoplanet Survey Satellite (TESS) are delivered in the form of full-frame images (FFIs). However, the FFIs contain systematic effects such as pointing jitter and scattered light from the Earth and Moon that must be removed (i.e., "detrended") before downstream analysis. We present unpopular, an open-source Python package to obtain detrended TESS FFI light curves optimized for variable sources. The unpopular package implements a variant of the causal pixel model to remove systematics and allows for simultaneous fitting with a polynomial component to capture nontransit astrophysical variations, such as supernova signals or stellar variability, that tend to be removed in techniques optimized for exoplanet detection. We validate our method by detrending different sources (e.g., supernovae, tidal disruption events (TDEs), exoplanet-hosting stars, fast-rotating stars) and comparing our light curves to those obtained by other pipelines when appropriate. Our supernova and TDE light curves are visually similar to those obtained by others using the ISIS image subtraction package, indicating that unpopular can be used to extract multisector light curves by preserving astrophysical signals on timescales of a TESS sector (~27 days). We note that our method contains tuning parameters that are currently set heuristically, and that the optimal set of tuning parameters will likely depend on the particular signal the user is interested in obtaining. The unpopular source code and tutorials are freely available online.

Keywords: Light curves, Astronomy data analysis, Transient sources, Exoplanet astronomy, Time domain astronomy, Variable stars, Linear regression, Transit photometry, Time series analysis
Earth as a Proxy Exoplanet: Simulating DSCOVR/EPIC Observations Using the Earth Spectrum Simulator. Analyzing time-resolved disk-integrated spectral images of the Earth can provide a baseline for future exoplanet characterization. The Earth Polychromatic Imaging Camera (EPIC) onboard the Deep Space Climate Observatory (DSCOVR) provides ~5000 full-disk sunlit Earth images each year in ten wavelengths from the ultraviolet to the near-infrared. A whole-disk radiative transfer model can improve our understanding of the temporal variation of Earth's disk-integrated reflected radiance ("light curves") at different wavelengths and create a pool of possible observations of Earth-like exoplanets. We use the two-stream-exact-single-scattering line-by-line radiative transfer model to build the Earth Spectrum Simulator (ESS) and reconstruct DSCOVR/EPIC spectral observations. Atmospheric effects, such as scattering by air molecules, clouds, aerosols, and gaseous absorption, are included. Surface contributions are treated using appropriate bidirectional reflectance distribution functions. We simulate ~300 images in each channel for observations collected in 2016, with a spatial resolution of ~2000 pixels over the visible disk. ESS provides a simultaneous fit to the observed light curves, with time-averaged reflectance differences typically less than 7% and root-mean-square errors less than 1%. The only exceptions are in the oxygen absorption channels, where reflectance biases can be as large as 19.55%; this is a consequence of simplified assumptions about clouds; especially their vertical placement. We also recover principal components of the spectrophotometric light curves and correlate them with atmospheric and surface features.

Keywords: Exoplanet atmospheric composition , Exoplanets, Exoplanet atmospheric variability, Earth (planet), Exoplanet surface variability, Exoplanet astronomy, Exoplanet surface composition, Radiative transfer, Exoplanet surface characteristics, Spectrophotometry, Habitable planets, Exoplanet atmospheres
TOI-1696 and TOI-2136: Constraining the Masses of Two Mini-Neptunes with the Habitable-Zone Planet Finder. We present the validation of two planets orbiting M dwarfs, TOI-1696b and TOI-2136b. Both planets are mini-Neptunes orbiting nearby stars, making them promising prospects for atmospheric characterization with the James Webb Space Telescope (JWST). We validated the planetary nature of both candidates using high-contrast imaging, ground-based photometry, and near-infrared radial velocities. Adaptive optics images were taken using the ShARCS camera on the 3 m Shane Telescope. Speckle images were taken using the NN-Explore Exoplanet Stellar Speckle Imager on the WIYN 3.5 m telescope. Radii and orbital ephemerides were refined using a combination of the Transiting Exoplanet Survey Satellite, the diffuser-assisted Astrophysical Research Consortium (ARC) Telescope Imaging Camera (ARCTIC) imager on the 3.5 m ARC telescope at Apache Point Observatory, and the 0.6 m telescope at Red Buttes Observatory. We obtained radial velocities using the Habitable-Zone Planet Finder on the 10 m Hobby-Eberly Telescope, which enabled us to place upper limits on the masses of both transiting planets. TOI-1696b (P = 2.5 days; R  p  = 3.24 R ⊕; M  p  &lt; 56.6 M ⊕) falls into a sparsely populated region of parameter space considering its host star's temperature (T eff = 3168 K, M4.5), as planets of its size are quite rare around mid- to late-M dwarfs. On the other hand, TOI-2136b (P = 7.85 days; R  p  = 2.09 R ⊕; M  p  &lt; 15.0 M ⊕) is an excellent candidate for atmospheric follow-up with the JWST.

Keywords: Exoplanets, Radial velocity, Gaussian Processes regression, Mini Neptunes, Transit photometry
Investigation on Doppler Imaging and Chromospheric Activity of the Young Dwarf LQ Hya Based on High-resolution Spectroscopy. We have obtained four Doppler images of LQ Hya in 2005 November-December, 2006 November-December, 2008 November, and 2014 January-February using high-resolution spectra obtained at three different observing sites. All of the surface maps show that the spots of LQ Hya are in bimodal distribution, i.e., in polar/high-latitude and low-latitude regions. Its chromospheric activity indicators exhibit obvious rotational modulations that are correlated with the simultaneous light curves, except in 2008. The correspondence between the maximum value of chromospheric emission and the low-latitude spot of new reconstructed image is clear, which indicates that both of them are driven by homologous magnetic field. The variation of H α  emission over a long time span suggests that the chromospheric plages may implicate a similar active cycle as photospheric spots.

Keywords: Starspots, Doppler imaging, Optical flares, Stellar activity
Precise Dynamical Masses of ∊ Indi Ba and Bb: Evidence of Slowed Cooling at the L/T Transition. We report individual dynamical masses of 66.92 ± 0.36 M Jup and 53.25 ± 0.29 M Jup for the binary brown dwarfs ∊ Indi Ba and Bb, measured from long-term (≍10 yr) relative orbit monitoring and absolute astrometry monitoring data on the Very Large Telescope (VLT). Relative astrometry with NACO fully constrains the Keplerian orbit of the binary pair, while absolute astrometry with FORS2 measures the system's parallax and mass ratio. We find a parallax consistent with the Hipparcos and Gaia values for ∊ Indi A, and a mass ratio for ∊ Indi Ba to Bb precise to better than 0.2%. ∊ Indi Ba and Bb have spectral types T1-1.5 and T6, respectively. With an age of ${3.5}_{-1.0}^{+0.8}$ Gyr from ∊ Indi A's activity, these brown dwarfs provide some of the most precise benchmarks for substellar cooling models. Assuming coevality, the very different luminosities of the two brown dwarfs and our moderate mass ratio imply a steep mass-luminosity relationship ( $L\propto {M}^{5.37\pm 0.08}$ ) that can be explained by a slowed cooling rate in the L/T transition, as previously observed for other L/T binaries. Finally, we present a periodogram analysis of the near-infrared photometric data, but find no definitive evidence of periodic signals with a coherent phase.

Keywords: Exoplanet dynamics, Brown dwarfs, Exoplanet astronomy, Astrometry, Orbit determination, T dwarfs
A Mini-Neptune from TESS and CHEOPS Around the 120 Myr Old AB Dor Member HIP 94235. The Transiting Exoplanet Survey Satellite (TESS) mission has enabled discoveries of the brightest transiting planet systems around young stars. These systems are the benchmarks for testing theories of planetary evolution. We report the discovery of a mini-Neptune transiting a bright star in the AB Doradus moving group. HIP 94235 (TOI-4399, TIC 464646604) is a V mag = 8.31 G-dwarf hosting a ${3.00}_{-0.28}^{+0.32}\,{R}_{\oplus }$ mini-Neptune in a 7.7 day period orbit. HIP 94235 is part of the AB Doradus moving group, one of the youngest and closest associations. Due to its youth, the host star exhibits significant photometric spot modulation, lithium absorption, and X-ray emission. Three 0.06% transits were observed during Sector 27 of the TESS Extended Mission, though these transit signals are dwarfed by the 2% peak-to-peak photometric variability exhibited by the host star. Follow-up observations with the Characterising Exoplanet Satellite confirmed the transit signal and prevented the erosion of the transit ephemeris. HIP 94235 is part of a 50 au G-M binary system. We make use of diffraction limited observations spanning 11 yr, and astrometric accelerations from Hipparcos and Gaia, to constrain the orbit of HIP 94235 B. HIP 94235 is one of the tightest stellar binaries to host an inner planet. As part of a growing sample of bright, young planet systems, HIP 94235 b is ideal for follow-up transit observations, such as those that investigate the evaporative processes driven by high-energy radiation that may sculpt the valleys and deserts in the Neptune population.

Keywords: Exoplanet astronomy, Exoplanet evolution, Exoplanet detection methods
Predicting the Exoplanet Yield of the TESS Prime and Extended Missions through Years 1-7. The Transiting Exoplanet Survey Satellite (TESS) has discovered ~5000 planets and planet candidates after 3.5 yr. With a planned second Extended Mission (EM2) spanning Years 5-7 on the horizon, now is the time to revise predictions of the TESS exoplanet yield. We present simulations of the number of detectable planets around 9.4 million AFGKM stars in the TESS Candidate Target List v8.01 through 7 yr of observations. Our simulations take advantage of improved models for the photometric performance, temporal window functions, and transit detection probability. We estimate that 4719 ± 334 planets should be detectable with the Prime Mission alone (Years 1-2), and another 3707 ± 209 should be detectable across the current Extended Mission (Years 3-4). Based on a proposed pointing scenario for EM2, we predict that TESS should find another 4093 ± 180 planets, bringing the total TESS yield to 12,519 ± 678. We provide our predicted yields as functions of host star spectral type, planet radius, orbital period, follow-up feasibility, and location relative to the habitable zone. As TESS continues, new planets will be progressively smaller, with longer orbital periods, and will orbit fainter stars. Half of the planets found in EM2 will be smaller than 4 R ⊕, and over 1200 will have orbital periods longer than 20 days, effectively doubling the TESS yields of both kinds of planets. The number of small (&lt;2 R ⊕) habitable-zone planets will also double, bringing the total TESS yield to 18 ± 5. We also compare our predictions to the actual Prime Mission yield, finding good agreement.

Keywords: Transit photometry, Exoplanets
Pyspeckit: A Spectroscopic Analysis and Plotting Package. pyspeckit is a toolkit and library for spectroscopic analysis in Python. We describe the pyspeckit package and highlight some of its capabilities, such as interactively fitting a model to data, akin to the historically widely-used splot function in IRAF. pyspeckit employs the Levenberg-Marquardt optimization method via the mpfit and lmfit implementations, and important assumptions regarding error estimation are described here. Wrappers to use pymc and emcee as optimizers are provided. A parallelized wrapper to fit lines in spectral cubes is included. As part of the astropy affiliated package ecosystem, pyspeckit is open source and open development, and welcomes input and collaboration from the community.

Keywords: Astronomy software, Spectroscopy
Correlated Read Noise Reduction in Infrared Arrays Using Deep Learning. We present a new procedure rooted in deep learning to construct science images from data cubes collected by astronomical instruments using HxRG detectors in low-flux regimes. It improves on the drawbacks of the conventional algorithms to construct 2D images from multiple readouts by using the readout scheme of the detectors to reduce the impact of correlated readout noise. We train a convolutional recurrent neural network on simulated astrophysical scenes added to laboratory darks to estimate the flux on each pixel of science images. This method achieves a reduction of the noise on constructed science images when compared to standard flux-measurement schemes (correlated double sampling, up-the-ramp sampling), which results in a reduction of the error on the spectrum extracted from these science images. Over simulated data cubes created in a low signal-to-noise ratio regime where this method could have the largest impact, we find that the error on our constructed science images falls faster than a $1/\sqrt{N}$ decay, and that the spectrum extracted from the images has, averaged over a test set of three images, a standard error reduced by a factor of 1.85 in comparison to the standard up-the-ramp pixel sampling scheme. The code used in this project is publicly available on GitHub 7 7 https://github.com/GuillaumePayeur/HxRG-denoiser

Keywords: Neural networks, Astronomical detectors, Astronomy data reduction, Near infrared astronomy
The TESS-Keck Survey. XI. Mass Measurements for Four Transiting Sub-Neptunes Orbiting K Dwarf TOI-1246. Multiplanet systems are valuable arenas for investigating exoplanet architectures and comparing planetary siblings. TOI-1246 is one such system, with a moderately bright K dwarf (V = 11.6, K = 9.9) and four transiting sub-Neptunes identified by TESS with orbital periods of 4.31, 5.90, 18.66, and 37.92 days. We collected 130 radial velocity observations with Keck/HIRES and TNG/HARPS-N to measure planet masses. We refit the 14 sectors of TESS photometry to refine planet radii (2.97 ± 0.06 R ⊕, 2.47 ± 0.08 R ⊕, 3.46 ± 0.09 R ⊕, and 3.72 ± 0.16 R ⊕) and confirm the four planets. We find that TOI-1246 e is substantially more massive than the three inner planets (8.1 ± 1.1 M ⊕, 8.8 ± 1.2 M ⊕, 5.3 ± 1.7 M ⊕, and 14.8 ± 2.3 M ⊕). The two outer planets, TOI-1246 d and TOI-1246 e, lie near to the 2:1 resonance (P e/P  d  = 2.03) and exhibit transit-timing variations. TOI-1246 is one of the brightest four-planet systems, making it amenable for continued observations. It is one of only five systems with measured masses and radii for all four transiting planets. The planet densities range from 0.70 ± 0.24 to 3.21 ± 0.44 g cm-3, implying a range of bulk and atmospheric compositions. We also report a fifth planet candidate found in the RV data with a minimum mass of 25.6 ± 3.6 M ⊕. This planet candidate is exterior to TOI-1246 e, with a candidate period of 93.8 days, and we discuss the implications if it is confirmed to be planetary in nature.

Keywords: Transits, Exoplanets, Radial velocity, Exoplanet systems, Exoplanet astronomy, Transit timing variation method, Mini Neptunes, Transit photometry
An Interferometric View of H-MM1. I. Direct Observation of NH<SUB>3</SUB> Depletion. Spectral lines of ammonia, NH3, are useful probes of the physical conditions in dense molecular cloud cores. In addition to advantages in spectroscopy, ammonia has also been suggested to be resistant to freezing onto grain surfaces, which should make it a superior tool for studying the interior parts of cold, dense cores. Here we present high-resolution NH3 observations with the Very Large Array and Green Bank Telescope toward a prestellar core. These observations show an outer region with a fractional NH3 abundance of X(NH3) = (1.975 ± 0.005) × 10-8 (±10% systematic), but it also reveals that, after all, the X(NH3) starts to decrease above a H2 column density of ≈2.6 × 1022 cm-2. We derive a density model for the core and find that the break point in the fractional abundance occurs at the density n(H2) ~ 2 × 105 cm-3, and beyond this point the fractional abundance decreases with increasing density, following the power law n -1.1. This power-law behavior is well reproduced by chemical models where adsorption onto grains dominates the removal of ammonia and related species from the gas at high densities. We suggest that the break-point density changes from core to core depending on the temperature and the grain properties, but that the depletion power law is anyway likely to be close to n -1 owing to the dominance of accretion in the central parts of starless cores.

Keywords: Interstellar molecules, Molecular clouds, Astrochemistry, Dense interstellar clouds, Star formation, Interstellar medium, Interferometry
The μ Arae Planetary System: Radial Velocities and Astrometry. With Hubble Space Telescope Fine Guidance Sensor astrometry and published and previously unpublished radial velocity measures, we explore the exoplanetary system μ Arae. Our modeling of the radial velocities results in improved orbital elements for the four previously known components. Our astrometry contains no evidence for any known companion but provides upper limits for three companion masses. A final summary of all past Fine Guidance Sensor exoplanet astrometry results uncovers a bias toward small inclinations (more face-on than edge-on). This bias remains unexplained by small number statistics, modeling technique, Fine Guidance Sensor mechanical issues, or orbit modeling of noise-dominated data. A numerical analysis using our refined orbital elements suggests that planet d renders the μ Arae system dynamically unstable on a timescale of 105 yr, in broad agreement with previous work.

Keywords: Exoplanets
Globally Optimal and Scalable N-way Matching of Astronomy Catalogs. Building on previous Bayesian approaches, we introduce a novel formulation of probabilistic cross-identification, where detections are directly associated to (hypothesized) astronomical objects in a globally optimal way. We show that this new method scales better for processing multiple catalogs than enumerating all possible candidates, especially in the limit of crowded fields, which is the most challenging observational regime for new-generation astronomy experiments such as the Rubin Observatory Legacy Survey of Space and Time. Here we study simulated catalogs where the ground truth is known and report on the statistical and computational performance of the method. The paper is accompanied by a public software tool to perform globally optimal catalog matching based on directional data.

Keywords: Bayes factor, Photometry, Astronomical methods, Catalogs