Sazuna/UAT_keywords huggingface dataset:
Revisiting the Transit Timing Variations in the TrES-3 and Qatar-1 Systems with TESS Data. We present and analyze 58 transit light curves of TrES-3b and 98 transit light curves of Qatar-1b, observed by the Transiting Exoplanet Survey Satellite, plus two transit light curves of Qatar-1b, observed by us, using a ground-based 1.23 m telescope. These light curves are combined with the best-quality light curves taken from the Exoplanet Transit Database and the literature. The precisely determined midtransit times from these light curves enable us to obtain the refined orbital ephemerides, with improved precision, for both hot Jupiters. From the timing analysis, we find indications of the presence of transit timing variations (TTVs) in both systems. Since the observed TTVs are unlikely to be short-term and periodic, the possibility of additional planets in orbits close to TrES-3b and Qatar-1b is ruled out. The possible causes of long-term TTVs, such as orbital decay, apsidal precession, the Applegate mechanism, and line-of-sight acceleration, are also examined. However, none of these possibilities are found to explain the observed TTV of TrES-3b. In contrast to this, line-of-sight acceleration appears to be a plausible explanation for the observed TTV of Qatar-1b. In order to confirm these findings, further high-precision transit and radial velocity observations of both systems would be worthwhile.

Keywords: Hot Jupiters, Exoplanets, Radial velocity, Transit timing variation method, Tidal interaction, Transit photometry
The Orbits of the Main Saturnian Satellites, the Saturnian System Gravity Field, and the Orientation of Saturn's Pole. Four spacecraft have been sent to investigate the Saturnian system: Pioneer 11, Voyager 1, Voyager 2, and Cassini. By analyzing data acquired with these spacecraft together with Earth-based and Hubble Space Telescope satellite astrometry and Saturnian ring and satellite occultations, we constructed a model for the orientation and precession of Saturn's pole and determined gravitational parameters of the system and the orbits of the Saturnian satellites. This article provides details of our analysis and its results. *

Keywords: Saturnian satellites
Fast Derivation of Contact Binary Parameters for Large Photometric Surveys. Thanks to an enormous release of light curves of contact binaries, it is a challenge to derive the parameters of contact binaries using the Phoebe program and the Wilson-Devinney program with the Markov chain Monte Carlo (MCMC) algorithm. In this paper, we use neural network (NN) and MCMC algorithm to derive the parameters of contact binaries. The fitting of models is still done with the MCMC algorithm, but that the neural network is used to establish the mapping relationship between the parameters and the light curves generated beforehand by Phoebe. The NN model is trained with a set of Phoebe-generated light curves with known input parameters, and then combined with the MCMC algorithm to quickly obtain the posterior distribution of the parameters. Two NN models without and with the influence of third light are established, which can generate light curves with 100 points faster than Phoebe by about four orders of magnitude under the same running condition. In addition, the two models can generate the light curves with an error of less than a millimagnitude. The feasibility of NN and MCMC algorithm is also verified by the synthetic light curves generated by Phoebe and the light curves from Kepler survey data. NN and MCMC algorithms can quickly derive the parameters and the corresponding parameter errors of contact binaries from sky survey. These parameters can also be used as more precise initial input values for the objectives of individual detailed studies.

Keywords: Eclipsing binary stars, Binary stars, Contact binary stars
Towards a Comprehensive View of Accretion, Inner Disks, and Extinction in Classical T Tauri Stars: An ODYSSEUS Study of the Orion OB1b Association. The coevolution of T Tauri stars and their surrounding protoplanetary disks dictates the timescales of planet formation. In this paper, we present magnetospheric accretion and inner disk wall model fits to near-UV (NUV) to near-IR (NIR) spectra of nine classical T Tauri stars in Orion OB1b as part of the Outflows and Disks around Young Stars: Synergies for the Exploration of ULLYSES Spectra (ODYSSEUS) survey. Using NUV-optical spectra from the Hubble UV Legacy Library of Young Stars as Essential Standards (ULLYSES) Director's Discretionary Program and optical-NIR spectra from the PENELLOPE VLT Large Programme, we find that the accretion rates of these targets are relatively high for the region's intermediate age of 5.0 Myr; rates are in the range of (0.5-17.2) × 10-8 M ☉ yr-1, with a median value of 1.2 × 10-8 M ☉ yr-1. The NIR excesses can be fit with 1200-1800 K inner disk walls located at 0.05-0.10 au from the host stars. We discuss the significance of the choice in extinction law, as the measured accretion rate depends strongly on the adopted extinction value. This analysis will be extended to the complete sample of T Tauri stars being observed through ULLYSES to characterize accretion and inner disks in star-forming regions of different ages and stellar populations.

Keywords: Very Large Telescope, Hubble Space Telescope, Reddening law, Pre-main sequence stars, Protoplanetary disks, Stellar accretion, Interstellar extinction, Stellar accretion disks
Extremely Low Mass Ratio Contact Binaries. I. The First Photometric and Spectroscopic Investigations of Ten Systems. The photometric and spectroscopic investigations of ten contact binaries were presented for the first time. It is discovered that the mass ratios of all the ten targets are smaller than 0.15, they are extremely low mass ratio contact binaries. Seven of them are deep contact binaries, two are medium contact binaries, while only one is a shallow contact system. Five of them show the O'Connell effect, and a dark spot on one of the two components can lead to a good fit of the asymmetric light curves. The orbital period studies of the ten binaries reveal that they all exhibit long-term period changes, six of them are increasing, while the others are shrinking. The LAMOST spectra were analyzed by the spectral subtraction method, and all the ten targets exhibit excess emissions in the H α  line, indicating chromospheric activity. The evolutionary states of the two components of the ten binaries were studied, and it is found that their evolutionary states are identical to those of the other contact binaries. Based on the study of the relation between orbital angular momentum and total mass, we discovered the ten systems may be at the late evolutionary stage of a contact binary. The initial masses of the two components and the ages of them were obtained. By calculating the instability parameters, we found that the ten contact binaries are relatively stable at present.

Keywords: Close binary stars, Stellar activity, Mass ratio, Eclipsing binary stars, Contact binary stars, Stellar evolution
Hubble WFC3 Spectroscopy of the Rocky Planet L 98-59 b: No Evidence for a Cloud-free Primordial Atmosphere. We are using archived data from HST of transiting exoplanet L 98-59 b to place constraints on its potentially hot atmosphere. We analyze the data from five transit visits and extract the final combined transmission spectrum using Iraclis. Then we use the inverse atmospheric retrieval code TauREx to analyze the combined transmission spectrum. There is a weak absorption feature near 1.40 μm and 1.55 μm in the transmission spectrum, which can be modeled by a cloudy atmosphere with abundant hydrogen cyanide (HCN). However, the unrealistically high abundance of HCN derived cannot be explained by any equilibrium chemical model with reasonable assumptions. Thus, the likeliest scenario is that L 98-59 b has a flat, featureless transmission spectrum in the WFC3/G141 bandpass due to a thin atmosphere with high mean molecular weight, an atmosphere with an opaque aerosol layer, or no atmosphere, and it is very unlikely for L 98-59 b to have a clear hydrogen-dominated primary atmosphere. Due to the narrow wavelength coverage and low spectral resolution of HST/WFC3 G141 grism observation, we cannot tell these different scenarios apart. Our simulation shows future higher precision measurements over wider wavelengths from the James Webb Space Telescope can be used to better characterize the planetary atmosphere of L 98-59 b.

Keywords: Extrasolar rocky planets, Exoplanet atmospheric composition , Exoplanets, Hubble Space Telescope, Exoplanet atmospheres
Revisiting the Iconic Spitzer Phase Curve of 55 Cancri e: Hotter Dayside, Cooler Nightside, and Smaller Phase Offset. Thermal phase curves of short-period exoplanets provide the best constraints on the atmospheric dynamics and heat transport in their atmospheres. The published Spitzer Space Telescope phase curve of 55 Cancri e, an ultra-short-period super-Earth, exhibits a large phase offset suggesting significant eastward heat recirculation, unexpected on such a hot planet. We present our rereduction and analysis of these iconic observations using the open source and modular Spitzer Phase Curve Analysis pipeline. In particular, we attempt to reproduce the published analysis using the same instrument detrending scheme as the original authors. We retrieve the dayside temperature ( ${T}_{\mathrm{day}}={3771}_{-520}^{+669}$ K), nightside temperature ( ${T}_{\mathrm{night}\,}\lt 1649$ K at 2σ), and longitudinal offset of the planet's hot spot, and quantify how they depend on the reduction and detrending. Our reanalysis suggests that 55 Cancri e has a negligible hot spot offset of $-{12}_{-18}^{+21}$ degrees east. The small phase offset and cool nightside are consistent with the poor heat transport expected on ultra-short-period planets. The high dayside 4.5 μm brightness temperature is qualitatively consistent with SiO emission from an inverted rock vapor atmosphere.

Keywords: Observational astronomy, Exoplanet atmospheric composition , Super Earths, Infrared telescopes
Search for Extraterrestrial Intelligence with the ngVLA. The next generation Very Large Array (ngVLA) will be the premiere centimeter-wave radio array in the Northern Hemisphere by the mid 2030s and thus has the potential to be one of the most effective instruments for the search for extraterrestrial intelligence (SETI). We show that, as of now, the ngVLA will be the only facility capable of detecting an extraterrestrial intelligence (ETI) signal generated by an Arecibo-like transmitter further than 300 pc. We present the optimal antenna array configurations and study the proposed frequency band coverage of the ngVLA and its implications to SETI. We argue for the ability to form of the order of 64 commensal high spectral resolution beams, as the large number of line of sights is critical to provide a competitive survey speed when compared to other modern surveys with telescopes such as MeerKAT and the future SKA. We advocate an Ethernet-based telescope architecture design for the ngVLA, which will provide a high degree of flexibility in SETI data analysis and will benefit the wider astronomy community through commensal science and open-source code, maximizing the potential scientific output of the ngVLA.

Keywords: Search for extraterrestrial intelligence, Technosignatures
X-Ray Emission from the Exoplanet Hosting LTT 1445 Triple Star System. JWST will be able to observe the atmospheres of rocky planets transiting nearby M dwarfs. The M-dwarf triple star system LTT 1445, at a distance of 6.86 pc, hosts some of the nearest rocky terrestrial planets. These planets most likely orbit the M 3.5V star LTT 1445A. During a 28.6 ks Chandra ACIS-S3 observation we have: (i) spatially resolved and detected all three stars in the LTT 1445 system; (ii) measured the X-ray luminosity of the individual stars, including LTT 1445A, for the first time; (iii) studied the flux variability of the X-ray sources and found strong variability from the A and C components; and (iv) investigated how the coronal luminosities, temperatures, and volume emission measures vary at different activity levels. Combining these X-ray data with upcoming HST ultraviolet observations will allow a differential emission measure estimation of the star's extreme-ultraviolet spectrum, thereby facilitating modeling of the rocky planets' atmospheres.

Keywords: M dwarf stars, Stellar x-ray flares, Planet hosting stars
Overview of the Instrumentation for the Dark Energy Spectroscopic Instrument. The Dark Energy Spectroscopic Instrument (DESI) embarked on an ambitious 5 yr survey in 2021 May to explore the nature of dark energy with spectroscopic measurements of 40 million galaxies and quasars. DESI will determine precise redshifts and employ the baryon acoustic oscillation method to measure distances from the nearby universe to beyond redshift z &gt; 3.5, and employ redshift space distortions to measure the growth of structure and probe potential modifications to general relativity. We describe the significant instrumentation we developed to conduct the DESI survey. This includes: a wide-field, 3.°2 diameter prime-focus corrector; a focal plane system with 5020 fiber positioners on the 0.812 m diameter, aspheric focal surface; 10 continuous, high-efficiency fiber cable bundles that connect the focal plane to the spectrographs; and 10 identical spectrographs. Each spectrograph employs a pair of dichroics to split the light into three channels that together record the light from 360–980 nm with a spectral resolution that ranges from 2000–5000. We describe the science requirements, their connection to the technical requirements, the management of the project, and interfaces between subsystems. DESI was installed at the 4 m Mayall Telescope at Kitt Peak National Observatory and has achieved all of its performance goals. Some performance highlights include an rms positioner accuracy of better than 0.″1 and a median signal-to-noise ratio of 7 of the [O II] doublet at 8 × 10‑17 erg s‑1 cm‑2 in 1000 s for galaxies at z = 1.4–1.6. We conclude with additional highlights from the on-sky validation and commissioning, key successes, and lessons learned.

Keywords: Spectrometers, Optical telescopes, Astronomical instrumentation, Spectroscopy, Dark energy
CLusters in the UV as EngineS (CLUES). I. Survey Presentation and FUV Spectral Analysis of the Stellar Light. The CLusters in the Uv as EngineS (CLUES) survey is a Cosmic Origins Spectrograph (COS) campaign aimed at acquiring the 1130-1770 Å rest-frame spectroscopy of very young (&lt;20 Myr) and massive (&gt;104 M ⊙) star clusters in galaxies that are part of the Hubble treasury program Legacy ExtraGalactic UV Survey. In this first paper of a series, we describe the CLUES sample consisting of 20 young star clusters and report their physical properties as derived by both multiwavelength photometry and far-UV (FUV) spectroscopy with Hubble Space Telescope. Thanks to the synergy of the two different data sets, we build a coherent picture of the diverse stellar populations found in each region (with sizes of 40-160 pc). We associate the FUV-brightest stellar population to the central targeted star cluster and the other modeled population to the diffuse stars that are included in the COS aperture. We observe better agreement between photometric and spectroscopic ages for star clusters younger than 5 Myr. For clusters older than 5 Myr, photometry and spectroscopy measurements deviate, with the latter producing older ages, due to the degeneracy of photometric models. FUV spectroscopy enables us to better constrain the stellar metallicities, a parameter that optical colors are insensitive to. Finally, the derived E(B - V) are quite similar, with a tendency for FUV spectroscopy to favor solutions with higher extinctions. The recovered masses are in agreement within a factor of 2 for all of the clusters.

Keywords: Observational astronomy, Young star clusters, Ultraviolet surveys
Debiasing the Minimum-mass Extrasolar Nebula: On the Diversity of Solid Disk Profiles. A foundational idea in the theory of in situ planet formation is the "minimum-mass extrasolar nebula" (MMEN), a surface density profile (Σ) of disk solids that is necessary to form the planets in their present locations. While most previous studies have fit a single power law to all exoplanets in an observed ensemble, it is unclear whether most exoplanetary systems form from a universal disk template. We use an advanced statistical model for the underlying architectures of multiplanet systems to reconstruct the MMEN. The simulated physical and Kepler-observed catalogs allow us to directly assess the role of detection biases, and in particular the effect of nontransiting or otherwise undetected planets, in altering the inferred MMEN. We find that fitting a power law of the form ${\rm{\Sigma }}={{\rm{\Sigma }}}_{0}^{* }{(a/{a}_{0})}^{\beta }$ to each multiplanet system results in a broad distribution of disk profiles; ${{\rm{\Sigma }}}_{0}^{* }={336}_{-291}^{+727}$ g cm-2 and $\beta =-{1.98}_{-1.52}^{+1.55}$ encompass the 16th-84th percentiles of the marginal distributions in an underlying population, where ${{\rm{\Sigma }}}_{0}^{* }$ is the normalization at a 0 = 0.3 au. Around half of the inner planet-forming disks have minimum solid masses of ≳ 40M ⊕ within 1 au. While transit observations do not tend to bias the median β, they can lead to both significantly over- and underestimated ${{\rm{\Sigma }}}_{0}^{* }$ and thus broaden the inferred distribution of disk masses. Nevertheless, detection biases cannot account for the full variance in the observed disk profiles; there is no universal MMEN if all planets formed in situ. The great diversity of solid disk profiles suggests that a substantial fraction (≳23%) of planetary systems experienced a history of migration.

Keywords: Extrasolar rocky planets, Exoplanets, Exoplanet systems, Planetary system formation, Protoplanetary disks, Exoplanet formation
Characterizing and Mitigating the Impact of Telluric Absorption in Precise Radial Velocities. Precise radial velocity (PRV) surveys are important for the search for Earth analogs around nearby bright stars, which induce a small stellar reflex motion with an RV amplitude of ~10 cm s-1. Detecting such a small RV signal poses challenges to instrumentation, data analysis, and the precision of astrophysical models to mitigate stellar jitter. In this work, we investigate an important component in the PRV error budget-the spectral contamination from the Earth's atmosphere (tellurics). We characterize the effects of telluric absorption on the RV precision and quantify its contribution to the RV error budget over time and across a wavelength range of 350 nm-2.5 μm. We use simulated solar spectra with telluric contamination injected, and we extract the RVs using two commonly adopted algorithms: dividing out a telluric model before performing cross-correlation or forward modeling the observed spectrum incorporating a telluric model. We assume various degrees of cleanness in removing the tellurics. We conclude that the RV errors caused by telluric absorption can be suppressed to close to or even below 1-10 cm s-1 in the blue optical region. At red through near-infrared wavelengths, however, the residuals of tellurics can induce an RV error on the meter-per-second level even under the most favorable assumptions for telluric removal, leading to significant systematic noise in the RV time series and periodograms. If the red-optical or near-infrared becomes critical in the mitigation of stellar activity, systematic errors from tellurics can be eliminated with a space mission such as EarthFinder.

Keywords: Earth atmosphere, Radial velocity, Astronomy data analysis, Exoplanet astronomy, Exoplanet detection methods
Correcting Stellar Flare Frequency Distributions Detected by TESS and Kepler. The habitability of planets is closely connected with stellar activity, mainly the frequency of flares and the distribution of flare energy. Kepler and TESS find many flaring stars via precise time-domain photometric data, and the frequency and energy distribution of stellar flares on different types of stars are studied statistically. However, the completeness and observational bias of detected flare events from different missions (e.g., Kepler and TESS) vary a lot. We use a unified data processing and detection method for flare events based on the light curves from Kepler and TESS. Then we perform injection and recovery tests in the original light curve of each star for each flare event to correct the completeness and energy of flares. Three samples of flaring stars are selected from Kepler and TESS, with rotation periods from 1 to ~5 days. Adopting a hot-blackbody assumption, our results show that the cumulative flare frequency distributions (FFDs) of the same stars in Kepler and TESS bands tend to be consistent after correction, revealing a more natural flaring frequency and energy distribution. Our results also extend the low-energy limit in cumulative FFD fitting to 1031.5-33 erg on different types of stars. For solar-type stars, the average power-law index of cumulative FFD (α cum) is -0.84, which indicates that low-energy flares contribute less to the total flare energy. With a piecewise correlation between α cum and T eff, α cum first rises from M2 to K1 stars, then slightly decreases for stars hotter than K1.

Keywords: Habitable zone, Stellar flares, Planet hosting stars, Stellar activity
Tolerance For the Pixelation Effect in Shear Measurement. Images taken by space telescopes typically have a superb spatial resolution, but a relatively poor sampling rate due to the finite CCD pixel size. Beyond the Nyquist limit, it becomes uncertain how much the pixelation effect may affect the accuracy of galaxy shape measurement. It is timely to study this issue given that a number of space-based large-scale weak lensing surveys are planned. Using the Fourier_Quad method, we quantify the shear recovery error as a function of the sampling factor Q, i.e., the ratio between the FWHM of the point-spread function (PSF) and the pixel size of the CCD, for different PSFs and galaxies of different sizes and noise levels. We show that sub-percent-level accuracy in shear recovery is achievable with single-exposure images for Q ≲ 2. The conclusion holds for galaxies much smaller than the PSF, and those with a significant level of noise.

Keywords: Weak gravitational lensing, Space telescopes, Gravitational lensing shear, Astronomy data analysis
Kepler and the Behemoth: Three Mini-Neptunes in a 40 Million Year Old Association. Stellar positions and velocities from Gaia are yielding a new view of open cluster dispersal. Here we present an analysis of a group of stars spanning Cepheus (l = 100°) to Hercules (l = 40°), hereafter the Cep-Her complex. The group includes four Kepler objects of interest: Kepler-1643 b (R p = 2.32 ± 0.13 R ⊕, P = 5.3 days), KOI-7368 b (R p = 2.22 ± 0.12 R ⊕, P = 6.8 days), KOI-7913 Ab (R p = 2.34 ± 0.18 R ⊕, P = 24.2 days), and Kepler-1627 Ab (R p = 3.85 ± 0.11 R ⊕, P = 7.2 days). The latter Neptune-sized planet is in part of the Cep-Her complex called the δ Lyr cluster. Here we focus on the former three systems, which are in other regions of the association. Based on kinematic evidence from Gaia, stellar rotation periods from TESS, and spectroscopy, these three objects are also ≈40 million years (Myr) old. More specifically, we find that Kepler-1643 is ${46}_{-7}^{+9}$ Myr old, based on its membership in a dense subcluster of the complex called RSG-5. KOI-7368 and KOI-7913 are ${36}_{-8}^{+10}$ Myr old, and are in a diffuse region that we call CH-2. Based on the transit shapes and high-resolution imaging, all three objects are most likely planets, with false-positive probabilities of 6 × 10-9, 4 × 10-3, and 1 × 10-4 for Kepler-1643, KOI-7368, and KOI-7913, respectively. These planets demonstrate that mini-Neptunes with sizes of ≈2 Earth radii exist at ages of 40 Myr.

Keywords: Exoplanet evolution, Open star clusters, Stellar ages, Stellar associations