Sazuna/UAT_keywords huggingface dataset:
The TESS-Keck Survey: Science Goals and Target Selection. The Kepler and TESS missions have demonstrated that planets are ubiquitous. However, the success of these missions heavily depends on ground-based radial velocity (RV) surveys, which combined with transit photometry can yield bulk densities and orbital properties. While most Kepler host stars are too faint for detailed follow-up observations, TESS is detecting planets orbiting nearby bright stars that are more amenable to RV characterization. Here, we introduce the TESS-Keck Survey (TKS), an RV program using ~100 nights on Keck/HIRES to study exoplanets identified by TESS. The primary survey aims are investigating the link between stellar properties and the compositions of small planets; studying how the diversity of system architectures depends on dynamical configurations or planet multiplicity; identifying prime candidates for atmospheric studies with JWST; and understanding the role of stellar evolution in shaping planetary systems. We present a fully automated target selection algorithm, which yielded 103 planets in 86 systems for the final TKS sample. Most TKS hosts are inactive, solar-like, main-sequence stars (4500 K ≤ T eff &lt;6000 K) at a wide range of metallicities. The selected TKS sample contains 71 small planets (R p ≤ 4 R ⊕), 11 systems with multiple transiting candidates, six sub-day-period planets and three planets that are in or near the habitable zone (S inc ≤ 10 S ⊕) of their host star. The target selection described here will facilitate the comparison of measured planet masses, densities, and eccentricities to predictions from planet population models. Our target selection software is publicly available and can be adapted for any survey that requires a balance of multiple science interests within a given telescope allocation. *The TESS-Keck Survey: Science Goals and Target Selection

Keywords: Observational astronomy, Exoplanet detection methods, Exoplanet catalogs, Exoplanets, Telescopes, Surveys, Fundamental parameters of stars, Exoplanet systems, Photometry, Spectroscopy, Radial velocity, Catalogs
TOI-1696: A Nearby M4 Dwarf with a 3 R <SUB>⊕</SUB> Planet in the Neptunian Desert. We present the discovery and validation of a temperate sub-Neptune around the nearby mid-M dwarf TIC 470381900 (TOI-1696), with a radius of 3.09 ± 0.11 R ⊕ and an orbital period of 2.5 days, using a combination of Transiting Exoplanets Survey Satellite (TESS) and follow-up observations using ground-based telescopes. Joint analysis of multiband photometry from TESS, Multicolor Simultaneous Camera for studying Atmospheres of Transiting exoplanets (MuSCAT), MuSCAT3, Sinistro, and KeplerCam confirmed the transit signal to be achromatic as well as refined the orbital ephemeris. High-resolution imaging with Gemini/'Alopeke and high-resolution spectroscopy with the Subaru InfraRed Doppler (IRD) confirmed that there are no stellar companions or background sources to the star. The spectroscopic observations with IRD and Infrared Telescope Facility SpeX were used to determine the stellar parameters, and it was found that the host star is an M4 dwarf with an effective temperature of T eff = 3185 ± 76 K and a metallicity of [Fe/H] = 0.336 ± 0.060 dex. The radial velocities measured from IRD set a 2σ upper limit on the planetary mass to be 48.8 M ⊕. The large radius ratio (R p/R ⋆ ~ 0.1) and the relatively bright near-infrared magnitude (J = 12.2 mag) make this planet an attractive target for further follow-up observations. TOI-1696 b is one of the planets belonging to the Neptunian desert with the highest transmission spectroscopy metric discovered to date, making it an interesting candidate for atmospheric characterizations with JWST.

Keywords: High resolution spectroscopy, Observational astronomy, Multi-color photometry, Transits, Exoplanet systems, Exoplanet astronomy, Photometry, Spectroscopy, Exoplanet detection methods, Transit photometry, Time series analysis
Reflected Spectroscopy of Small Exoplanets II: Characterization of Terrestrial Exoplanets. A space telescope capable of high-contrast imaging has been recognized as the avenue toward finding terrestrial planets around nearby Sun-like stars and characterizing their potential habitability. It is thus essential to quantify the capability of reflected light spectroscopy obtained through direct imaging for terrestrial exoplanets, and existing work focused on planetary analogs of modern Earth. Here we go beyond Earth analogs and use a Bayesian retrieval algorithm, EXOREL ${}^{{\mathfrak{R}}}$ , to determine what we could learn about terrestrial exoplanets from their reflected light spectra. Recognizing the potential diversity of terrestrial exoplanets, our focus is to distinguish atmospheric scenarios without any a priori knowledge of the dominant gas. We find that, while a moderate-resolution spectrum in the optical band (0.4-1.0 μm) may sufficiently characterize a modern Earth analog, it would likely result in incorrect interpretation for planets similar to Archean Earth or having CO2-dominated atmospheres. Including observations in the near-infrared bands (1.0-1.8 μm) can prevent this error, determine the main component (N2, O2, or CO2), and quantify trace gases (H2O, O3, and CH4) of the atmosphere. These results are useful to define the science requirements and design the wavelength bandwidth and observation plans of exoplanet direct imaging missions in the future.

Keywords: Extrasolar rocky planets, Exoplanet atmospheric composition , Bayesian statistics, Posterior distribution, Bayes' Theorem, Prior distribution, Exoplanet atmospheres
Hubble Space Telescope STIS Spectroscopy of Nova T Aurigae 1891. T Aurigae is an eclipsing old nova that exploded in 1891. At a Gaia EDR3 distance of 815-871 pc, it is a relatively nearby old nova. Through ultraviolet spectral modeling and using the new precise Gaia distance, we find that the HST/STIS spectrum of T Aurigae is consistent with an accretion disk with a mass-transfer rate $\dot{M}$ of the order of 10-8 M ⊙ yr-1, for a white-dwarf mass of M wd ≈ 0.7 ± 0.2M ⊙, an inclination of i ~ 60°, and a Gaia distance of of ${840}_{-25}^{+31}$ pc. The sharp absorption lines of metals cannot form in the disk and are likely forming in material above the disk (e.g., due stream disk overflow), in circumbinary material, and/or in material associated with the ejected shell from the 1891 nova explosion. The saturated hydrogen Lyα absorption feature is attributed to a large interstellar-medium hydrogen-column density of the order of 1021cm-2 toward T Aur, as corroborated by the value of its reddening E(B - V) = 0.42 ± 0.08.

Keywords: Cataclysmic variable stars, Classical novae
The Lingering Death of Periodic Near-Sun Comet 323P/SOHO. We observed near-Sun comet 323P/SOHO for the first time using ground and space telescopes. In late 2020 December, the object was recovered at Subaru showing no cometary features on its way to perihelion. However, in our postperihelion observations, it developed a long narrow tail mimicking a disintegrated comet. The ejecta, composed of at least millimeter-sized dust with power-law size distribution index 3.2 ± 0.2, was impulsively produced shortly after the perihelion passage, during which ≳0.1%-10% of the nucleus mass was shed due to excessive thermal stress and rotational disruption. Two fragments of ~20 m in radius (assuming a geometric albedo of 0.15) were seen in Hubble Space Telescope observations from early 2021 March. The nucleus, with an effective radius of 86 ± 3 m (the same albedo assumed) and an aspect ratio of ~0.7, has a rotation period of 0.522 hr, which is the shortest for known comets in the solar system and implies cohesive strength ≳10-100 Pa in the interior. The color of the object was freakish and changed temporally in a never-before-seen manner. Using our astrometry, we found a strong nongravitational effect following a heliocentric dependency of ${r}_{{\rm{H}}}^{-8.5}$ in the transverse motion of the object. Our N-body integration reveals that 323P has a likelihood of 99.7% to collide with the Sun in the next two millennia driven by the ν 6 secular resonance.

Keywords: Sundivers, Near-Earth objects, Small Solar System bodies, Comets, Sunskirters
The Transmission Spectrum of WASP-17 b From the Optical to the Near-infrared Wavelengths: Combining STIS, WFC3, and IRAC Data Sets. We present the transmission spectrum of the inflated hot Jupiter WASP-17 b, observed with the STIS and WFC3 instruments aboard the Hubble Space Telescope, allowing for a continuous wavelength coverage from ~0.4 to ~1.7 μm. Observations taken with IRAC channels 1 and 2 on the Spitzer Space Telescope are also included, adding photometric measurements at 3.6 and 4.5 μm. HST spectral data were analyzed with Iraclis, a pipeline specialized in the reduction of STIS and WFC3 transit and eclipse observations. Spitzer photometric observations were reduced with the TLCD-LSTM method, utilizing recurrent neural networks. The outcome of our reduction produces incompatible results between STIS visit 1 and visit 2, which leads us to consider two scenarios for G430L. Additionally, by modeling the WFC3 data alone, we can extract atmospheric information without having to deal with the contrasting STIS data sets. We run separate retrievals on the three spectral scenarios with the aid of TauREx 3, a fully Bayesian retrieval framework. We find that, independently of the data considered, the exoplanet atmosphere displays strong water signatures and, potentially, the presence of aluminum oxide and titanium hydride. A retrieval that includes an extreme photospheric activity of the host star is the preferred model, but we recognize that such a scenario is unlikely for an F6-type star. Due to the incompleteness of all STIS spectral light curves, only further observations with this instrument would allow us to properly constrain the atmospheric limb of WASP-17 b, before the James Webb Space Telescope or Ariel will come online.

Keywords: Hubble Space Telescope, Bayesian statistics, Astronomy data reduction, Exoplanet atmospheres
Discovery of 34 Low-mass Comoving Systems Using NOIRLab Source Catalog DR2. We present the discovery of 34 comoving systems containing an ultracool dwarf found by means of the NOIRLab Source Catalog (NSC) DR2. NSC's angular resolution of ~ 1″ allows for the detection of small separation binaries with significant proper motions. We used the catalog's accurate proper motion measurements to identify the companions by cross-matching a previously compiled list of brown dwarf candidates with NSC DR2. The comoving pairs consist of either a very low-mass star and an ultracool companion, or a white dwarf and an ultracool companion. The estimated spectral types of the primaries are in the K and M dwarf regimes, those of the secondaries in the M, L, and T dwarf regimes. We calculated angular separations between ~2″ and ~ 56″, parallactic distances between ~43 and ~261 pc, and projected physical separations between ~169 and ~8487 au. The lowest measured total proper motion is 97 mas yr-1, with the highest 314 mas yr-1. Tangential velocities range from ~23 to ~187 km s-1. We also determined comoving probabilities, estimated mass ratios, and calculated binding energies for each system. We found no indication of possible binarity for any component of the 34 systems in the published literature. The discovered systems can contribute to the further study of the formation and evolution of low-mass systems as well as to the characterization of cool substellar objects.

Keywords: Multiple stars, Brown dwarfs, Binary stars, White dwarf stars, Low mass stars
Analytic Light Curves in Reflected Light: Phase Curves, Occultations, and Non-Lambertian Scattering for Spherical Planets and Moons. We derive efficient, closed-form, differentiable, and numerically stable solutions for the flux measured from a spherical planet or moon seen in reflected light, either in or out of occultation. Our expressions apply to the computation of scattered light phase curves of exoplanets, secondary eclipse light) curves in the optical, or future measurements of planet-moon and planet-planet occultations, as well as to photometry of solar system bodies. We derive our solutions for Lambertian bodies illuminated by a point source, but extend them to model illumination sources of finite angular size and rough surfaces with phase-dependent scattering. Our algorithm is implemented in Python within the open-source starry mapping framework and is designed with efficient gradient-based inference in mind. The algorithm is ~4-5 orders of magnitude faster than direct numerical evaluation methods and ~10 orders of magnitude more precise. We show how the techniques developed here may one day lead to the construction of two-dimensional maps of terrestrial planet surfaces, potentially enabling the detection of continents and oceans on exoplanets in the habitable zone. 6 6 https://github.com/rodluger/starrynight

Keywords: Eclipses, Exoplanets, Light curves, Analytical mathematics, Occultation
The Intrinsic Multiplicity Distribution of Exoplanets Revealed from the Radial Velocity Method. Planet multiplicities are useful in constraining the formation and evolution of planetary systems, but they are usually difficult to constrain observationally. Here, we develop a general method that can properly take into account the survey incompleteness and recover the intrinsic planet multiplicity distribution. We then apply it to the radial velocity (RV) planet sample from the California Legacy Survey (CLS). Within the 1 au (10 au) region, we find 21% ± 4% (19.2% ± 2.8%) of Sun-like stars host planets with masses above 10 M ⊕ (0.3 M J), about 30% (40%) of which are multiplanet systems; in terms of the RV semi-amplitude K, 33% ± 7% (25% ± 3%) of Sun-like stars contain planets of K &gt; 1 m s-1 (3 m s-1), and each system hosts on average 1.8 ± 0.4 (1.63 ± 0.16) planets. We note that the hot Jupiter rate in the CLS Sun-like sample is higher than the consensus value of ~1% by a factor of about three. We also confirm previous studies on the correlation between inner ( &lt;1 au) and outer ( &gt;1 au) planets.

Keywords: Radial velocity, Exoplanet systems, Exoplanets
Incorporating Measurement Error in Astronomical Object Classification. Most general-purpose classification methods, such as support-vector machine (SVM) and random forest (RF), fail to account for an unusual characteristic of astronomical data: known measurement error uncertainties. In astronomical data, this information is often given in the data but discarded because popular machine learning classifiers cannot incorporate it. We propose a simulation-based approach that incorporates heteroscedastic measurement error into an existing classification method to better quantify uncertainty in classification. The proposed method first simulates perturbed realizations of the data from a Bayesian posterior predictive distribution of a Gaussian measurement error model. Then, a chosen classifier is fit to each simulation. The variation across the simulations naturally reflects the uncertainty propagated from the measurement errors in both labeled and unlabeled data sets. We demonstrate the use of this approach via two numerical studies. The first is a thorough simulation study applying the proposed procedure to SVM and RF, which are well-known hard and soft classifiers, respectively. The second study is a realistic classification problem of identifying high-z (2.9 ≤ z ≤ 5.1) quasar candidates from photometric data. The data are from merged catalogs of the Sloan Digital Sky Survey, the Spitzer IRAC Equatorial Survey, and the Spitzer-HETDEX Exploratory Large-Area Survey. The proposed approach reveals that out of 11,847 high-z quasar candidates identified by a random forest without incorporating measurement error, 3146 are potential misclassifications with measurement error. Additionally, out of 1.85 million objects not identified as high-z quasars without measurement error, 936 can be considered new candidates with measurement error.

Keywords: Astrostatistics tools, Bayesian statistics, Classification, Quasars, Astrostatistics techniques
The First High-contrast Images of X-Ray Binaries: Detection of Candidate Companions in the γ Cas Analog RX J1744.7-2713. X-ray binaries provide exceptional laboratories for understanding the physics of matter under the most extreme conditions. Until recently, there were few, if any, observational constraints on the circumbinary environments of X-ray binaries at ~100-5000 au scales. It remains unclear how the accretion onto the compact objects or the explosions giving rise to the compact objects interact with their immediate surroundings. Here, we present the first high-contrast adaptive optics images of X-ray binaries. These observations target all X-ray binaries within ~3 kpc accessible with the Keck/NIRC2 vortex coronagraph. This paper focuses on one of the first key results from this campaign; our images reveal the presence of 21 sources potentially associated with the γ Cassiopeiae analog high-mass X-ray binary RX J1744.7-2713. By conducting different analyses-a preliminary proper motion analysis, a color-magnitude diagram, and a probability of chance alignment calculation-we found that three of these 21 sources have a high probability of being bound to the system. If confirmed, they would be in wide orbits (~450 to 2500 au). While follow-up astrometric observations will be needed in ~5-10 yr to confirm further the bound nature of these detections, these discoveries emphasize that such observations may provide a major breakthrough in the field. In fact, they would be useful not only for our understanding of stellar multiplicity, but also for our understanding of how planets, brown dwarfs, and stars can form even in the most extreme environments.

Keywords: Multiple stars, X-ray binary stars, High mass x-ray binary stars, Infrared astronomy, Coronagraphic imaging, Direct imaging
Coronal and Chromospheric Emission in A-type Stars. Cool stars on the main sequence generate X-rays from coronal activity, powered by a convective dynamo. With increasing temperature, the convective envelope becomes smaller and X-ray emission fainter. We present Chandra/HRC-I observations of four single stars with early A spectral types. Only the coolest star of this sample, τ 3 Eri (T eff ≈ 8, 000 K), is detected with $\mathrm{log}({L}_{X}/{L}_{\mathrm{bol}})=-7.6$ while the three hotter stars (T eff ≥ 8, 000 K), namely δ Leo, β Leo, and ι Cen, remain undetected with upper limits $\mathrm{log}({L}_{X}/{L}_{\mathrm{bol}})\lt -8.4$ . The drop in X-ray emission thus occurs in a narrow range of effective temperatures around ~8100 K and matches the drop of activity in the C III and O VI transition region lines.

Keywords: A stars, Stellar atmospheres, Stellar activity
The COS CGM Compendium. IV. Effects of Varying Ionization Backgrounds on Metallicity Determinations in the z &lt; 1 Circumgalactic Medium. Metallicity estimates of circumgalactic gas based on absorption-line measurements typically require photoionization modeling to account for unseen ionization states. We explore the impact of uncertainties in the extreme-ultraviolet background (EUVB) radiation on such metallicity determinations for the z &lt; 1 circumgalactic medium. In particular, we study how uncertainties in the power-law slope of the EUV radiation, α EUVB, from active galactic nuclei affect metallicity estimates in a sample of 34 absorbers with H I column densities between $15.25\lt \mathrm{log}({N}_{{\rm{H}}\,{\rm\small{I}}}/{\mathrm{cm}}^{-2})\lt 17.25$ and measured metal ion column densities. We demonstrate the sensitivity of metallicity estimates to changes in the EUV power-law slope of active galactic nuclei, α EUVB, at low redshift (z &lt; 1), showing that derived absorber metallicities increase on average by ≈0.3 dex as the EUV slope is hardened from α EUVB = -2.0 to -1.4. We use Markov Chain Monte Carlo sampling of photoionization models with α EUVB as a free parameter to derive metallicities for these absorbers. The current sample of absorbers does not provide a robust constraint on the slope α EUVB itself; we discuss how future analyses may provide stronger constraints. Marginalizing over the uncertainty in the slope of the background, we find that the average uncertainties in the metallicity determinations increase from 0.08 to 0.14 dex when switching from a fixed EUVB slope to one that freely varies. Thus, we demonstrate that EUVB uncertainties can be included in ionization models while still allowing for robust metallicity inferences.

Keywords: Intergalactic medium, Lyman limit systems, Quasar absorption line spectroscopy, Circumgalactic medium
How Do Spitzer IRAC Fluxes Compare to HST CALSPEC?. An accurate tabulation of stellar brightness in physical units is essential for a multitude of scientific endeavors. The HST/CALSPEC database of flux standards contains many stars with spectral coverage in the 0.115-1 μm range, with some extensions to longer wavelengths of 1.7 or 2.5 μm. Modeled flux distributions to 32 μm for calibration of JWST complement the shorter-wavelength HST measurements. Understanding the differences between IRAC observations and CALSPEC models is important for science that uses IR fluxes from multiple instruments, including JWST. The absolute flux of Spitzer IRAC photometry at 3.6-8 μm agrees with CALSPEC synthetic photometry to 1% for the three prime HST standards: G191B2B, GD153, and GD71. For a set of 17-22 A-star standards, the average IRAC difference rises from agreement at 3.6 μm to 3.4% ± 0.1% brighter than CALSPEC at 8 μm. For a smaller set of G-type stars, the average of the IRAC photometry falls below CALSPEC by as much as 3.7% ± 0.3% for IRAC1, while one G-type star, P330E, is consistent with the A-star ensemble of IRAC/CALSPEC ratios.

Keywords: Spectrophotometric standards, Infrared photometry, Flux calibration
Probing TYC 3315-1807-1, An sdB+dM Binary Displaying Strong Period Variation and Reflection Effect. Subdwarf (sdB) stars include core helium-burning stars with a very thin hydrogen envelope that lies at the blue end of the horizontal branch (or extreme horizontal branch). Among them, short-period sdB binaries especially with cool companions are significant to test and constrain binary evolution. We discuss one such sdB+dM type binary, TYC 3315-1807-1 (V1), which was first reported by Kawka. Results of the photometric analysis on Transiting Exoplanet Survey Satellite data are being reported. Light variation in the light curve suggests that the system displays a large reflection effect with no eclipses. Spectroscopic observations of the object were also carried out to probe into the nature of secondary companion as well as to understand the post-common-envelope evolution of such objects. The variability in Balmer, He, and Na line profiles as a function of phase, probably caused by observed reflection effect was identified and studied. Period variation study of the object was done using times of minima obtained from the literature and the O - C plot was produced, which points to a decrease in the period (dp/dt = -1.36315 × 10-7 day yr-1), and the possible scenario of evolution is discussed. From the evolutionary models, we constrain the possible mass of the sdB to be 0.274 M ⊙ and that of the secondary is 0.113 M ⊙, and we conclude that V1 may evolve directly as a helium-core white dwarf.

Keywords: Binary stars