Sazuna/UAT_keywords huggingface dataset:
Uncertainty of Line-of-sight Velocity Measurements of Faint Stars from Low- and Medium-resolution Optical Spectra. Massively multiplexed spectrographs will soon gather large statistical samples of stellar spectra. The accurate estimation of uncertainties on derived parameters, such as the line-of-sight velocity v los, especially for spectra with low signal-to-noise ratios (S/Ns), is paramount. We generated an ensemble of simulated optical spectra of stars as if they were observed with low- and medium-resolution fiber-fed instruments on an 8 m class telescope, similar to the Subaru Prime Focus Spectrograph, and determined v los by fitting stellar templates to the simulated spectra. We compared the empirical errors of the derived parameters—calculated from an ensemble of simulations—to the asymptotic errors determined from the Fisher matrix, as well as from Monte Carlo sampling of the posterior probability. We confirm that the uncertainty of v los scales with the inverse square root of the S/N, but also show how this scaling breaks down at low S/N and analyze the error and bias caused by template mismatch. We outline a computationally optimized algorithm to fit multiexposure data and provide a mathematical model of stellar spectrum fitting that maximizes the so called significance, which allows for calculating the error from the Fisher matrix analytically. We also introduce the effective line count, and provide a scaling relation to estimate the errors of v los measurements based on stellar type. Our analysis covers a range of stellar types with parameters that are typical of the Galactic outer disk and halo, together with analogs of stars in M31 and in satellite dwarf spheroidal galaxies around the Milky Way.

Keywords: Late-type stars, Galactic archaeology, Spectroscopy, Late-type giant stars, Radial velocity, Doppler shift
HST SHEL: Enabling Comparative Exoplanetology with HST/STIS. The Hubble Space Telescope (HST) has been our most prolific tool to study exoplanet atmospheres. As the age of JWST begins, there are a wealth of HST archival data that are useful to strengthen our inferences from JWST. Notably, HST/Space Telescope Imaging Spectrograph (STIS), with its 0.3–1 μm wavelength coverage, extends past JWST's 0.6 μm wavelength cutoff and holds an abundance of potential information: alkali (Na, K) and molecular (TiO, VO) species opacities, aerosol information, and the presence of stellar contamination. However, time-series observations with HST suffer from significant instrumental systematics and can be highly dependent on choices made during the transit fitting process. This makes comparing transmission spectra of planets with different data reduction methodologies challenging, as it is difficult to discern whether an observed trend is caused by differences in data reduction or underlying physical processes. Here we present the Sculpting Hubble's Exoplanet Legacy (SHEL) program, which aims to build a consistent data reduction and light-curve analysis methodology and associated database of transmission spectra from archival HST observations. In this paper, we present the SHEL analysis framework for HST/STIS and its low-resolution spectroscopy modes, G430L and G750L. We apply our methodology to four notable hot Jupiters, WASP-39 b, WASP-121 b, WASP-69 b, and WASP-17 b, and use these examples to discuss nuances behind analysis with HST/STIS. Our results for WASP-39 b, WASP-121 b, and WASP-17 b are consistent with past publications, but our analysis of WASP-69 b differs and shows evidence of either a strong scattering slope or stellar contamination. The data reduction pipeline and tutorials are available on Github and Zenodo.

Keywords: Hot Jupiters, Exoplanet atmospheres, Astronomy data reduction, Exoplanets
A Relativistic Framework to Estimate Clock Rates on the Moon. As humanity aspires to explore the solar system and investigate distant worlds such as the Moon, Mars, and beyond, there is a growing need to estimate and model the rate of clocks on these celestial bodies and compare them with the rate of standard clocks on Earth. According to Einstein's theory of relativity, the rate of a standard clock is influenced by the gravitational potential at its location and its relative motion. A convenient choice of local reference frames allows for the comparison of local time variations of clocks due to gravitational and kinematic effects. We estimate the rate of clocks on the Moon using a locally freely falling reference frame coincident with the center of mass of the Earth–Moon system. A clock near the Moon's selenoid ticks faster than one near the Earth's geoid, accumulating an extra 56.02 μs day‑1 over the duration of a lunar orbit. This formalism is then used to compute the clock rates at Earth–Moon Lagrange points. Accurate estimation of the rate differences of coordinate times across celestial bodies and their intercomparisons using clocks on board orbiters at Lagrange points as time transfer links is crucial for establishing reliable communications infrastructure. This understanding also underpins precise navigation in cislunar space and on celestial bodies' surfaces, thus playing a pivotal role in ensuring the interoperability of various position, navigation, and timing systems spanning from Earth to the Moon and to the farthest regions of the inner solar system.

Keywords: Gravitation, Celestial mechanics, The Moon, Earth (planet)
Evidence for a Shallow Evolution in the Volume Densities of Massive Galaxies at z = 4–8 from CEERS. We analyze the evolution of massive (log10[M ⋆/M ⊙] &gt; 10) galaxies at z ∼ 1–4 selected from JWST Cosmic Evolution Early Release Survey (CEERS). We infer the physical properties of all galaxies in the CEERS NIRCam imaging through spectral energy distribution (SED) fitting with dense basis to select a sample of high-redshift massive galaxies. Where available we include constraints from additional CEERS observing modes, including 18 sources with MIRI photometric coverage, and 28 sources with spectroscopic confirmations from NIRSpec or NIRCam WFSS. We sample the recovered posteriors in stellar mass from SED fitting to infer the volume densities of massive galaxies across cosmic time, taking into consideration the potential for sample contamination by active galactic nuclei. We find that the evolving abundance of massive galaxies tracks expectations based on a constant baryon conversion efficiency in dark matter halos for z ∼ 1–4. At higher redshifts, we observe an excess abundance of massive galaxies relative to this simple model, resulting in a shallower decline of observed volume densities of massive galaxies. These higher abundances can be explained by modest changes to star formation physics and/or the efficiencies with which star formation occurs in massive dark matter halos, and are not in tension with modern cosmology.

Keywords: Galaxy formation, High-redshift galaxies, Galaxy evolution, Galactic and extragalactic astronomy
Following the Pulsations in the Long-term Cooling of GW Librae and V386 Serpentis. GW Lib and V386 Ser are dwarf novae systems containing pulsating white dwarfs that underwent large 8─9 mag amplitude outbursts in 2007 and 2019, respectively. Following the pulsation periods in these systems after the outburst provides a means to view the heating and cooling effects of mass accretion on the instability region of the white dwarf. Follow-up optical observations during 2021─2023 for these two systems are reported, resulting in a time span coverage of 16 yr for GW Lib and 4 yr for V386 Ser after their outbursts that reveal large differences in behavior as their white dwarfs returned to quiescence. GW Lib showed intermittent longer periods at 19 minutes, 1.4, 2, and 4 hr during the first 16 yr after the outburst, before finally showing, at 14 yr post-outburst, two of the three short-period modes apparent during preoutburst quiescence. In contrast, V386 Ser appeared to follow theoretical expectations, showing a shorter-period pulsation soon after the outburst, and progressively longer periods as it cooled to its quiescent state. While the optical light returns to quiescent value within 2 yr, it is apparent that the white dwarf takes much longer to recover to its quiescent state. Theoretical work is needed to explain the large differences in otherwise similar systems.

Keywords: White dwarf stars
Different Planetary Eccentricity-period (PEP) Distributions of Small and Giant Planets. We used the database of 1040 short-period (1 ≤ P &lt; 200 days) exoplanets radial-velocity orbits to study the planetary eccentricity-period (PEP) distribution. We first divided the sample into low- and high-mass exoplanet subsamples based on the distribution of the (minimum) planetary masses, which displays a clear two-Gaussian distribution, separated at 0.165M J. We then selected 216 orbits, low- and high-mass alike, with eccentricities significantly distinct from circular orbits. The 131 giant-planet eccentric orbits display a clear upper envelope, which we model quantitatively, rises monotonically from zero eccentricity and reaches an eccentricity of 0.8 at P ∼ 100 days. Conversely, the 85 low-mass planetary orbits display a flat eccentricity distribution between 0.1 and 0.5, with almost no dependence on the orbital period. We show that the striking difference between the two PEP distributions is not a result of the detection technique used. The upper envelope of the high-mass planets, also seen in short-period binary stars, is a clear signature of tidal circularization, which probably took place inside the planets, while the small-planet PEP distribution suggests that the circularization was not effective, probably due to dynamical interactions with neighboring planets.

Keywords: Exoplanet dynamics, Exoplanets, Astrostatistics techniques, Exoplanet evolution, Exoplanet tides
Evidence for Primordial Alignment: Insights from Stellar Obliquity Measurements for Compact Sub-Saturn Systems. Despite decades of effort, the mechanisms by which the spin axis of a star and the orbital axes of its planets become misaligned remain elusive. In particular, it is of great interest whether the large spin–orbit misalignments observed are driven primarily by high-eccentricity migration—expected to have occurred for short-period, isolated planets—or reflect a more universal process that operates across systems with a variety of present-day architectures. Compact multiplanet systems offer a unique opportunity to differentiate between these competing hypotheses, as their tightly packed configurations preclude violent dynamical histories, including high-eccentricity migration, allowing them to trace the primordial disk plane. In this context, we report measurements of the sky-projected stellar obliquity (λ) via the Rossiter–McLaughlin effect for two sub-Saturns in multiple-transiting systems: TOI-5126 b (λ = 1 ± 48°) and TOI-5398 b ( ). Both are spin–orbit aligned, joining a fast-growing group of just three other compact sub-Saturn systems, all of which exhibit spin–orbit alignment. In aggregate with archival data, our results strongly suggest that sub-Saturn systems are primordially aligned and become misaligned largely in the postdisk phase, as appears to be the case increasingly for other exoplanet populations.

Keywords: Exoplanet dynamics, Transits, Exoplanet astronomy, Exoplanet evolution, Radial velocity, Extrasolar gaseous giant planets
Electron Density Distribution in H II Regions in IC 10. We present the [O III] λ52 μm map of the dwarf galaxy IC 10 obtained with the Field-Imaging Far-Infrared Line Spectrometer on board the Stratospheric Observatory for Infrared Astronomy. We combine the [O III] λ52 μm map with Herschel and Spitzer observations to estimate the electron density distribution of the brightest H II regions of IC 10. We find that the line ratio [O III] λ88 μm/[O III] λ52 μm gives electron density (n e) values (n e [O III]) that cover a broad range, while the n e values obtained using the line ratio [S III] λ33 μm/[S III] λ18 μm (n e [S III]) are all similar within the uncertainties. n e [O III] is similar to n e [S III] for the M1, M2, and A1 regions, and it is higher than n e [S III] for the two regions, A2 and M1b, which are the brightest in the 24 μm continuum emission. These results suggest that for these regions, the two ions, O++ and S++, trace two different ionized gas components and that the properties of the ionized gas component traced by the O++ ion are more sensitive to the local physical conditions. In fact, while the gas layer traced by [S III] does not keep track of the characteristics of the radiation field, the n e [O III] correlates with the star formation rate, the dust temperature, and the 24 μm. Therefore, n e [O III] is an indicator of the evolutionary stage of the H II region and the radiation field, with higher n e [O III] found in younger star-forming regions and in more energetic environments.

Keywords: Dwarf galaxies, Interstellar medium
Trials and Tribulations in the Reanalysis of KELT-24 b: A Case Study for the Importance of Stellar Modeling. We present a new analysis of the KELT-24 system, comprising a well-aligned hot Jupiter, KELT-24 b, and a bright (V = 8.3), nearby (d = 96.9 pc) F-type host star. KELT-24 b was independently discovered by two groups in 2019, with each reporting best-fit stellar parameters that were notably inconsistent. Here, we present three independent analyses of the KELT-24 system, each incorporating a broad range of photometric and spectroscopic data, including eight sectors of Transiting Exoplanet Survey Satellite (TESS) photometry and more than 200 new radial velocities (RVs) from the MINiature Exoplanet Radial Velocity Array. Two of these analyses use KELT-24's observed spectral energy distribution (SED) through a direct comparison to stellar evolutionary models, while our third analysis assumes an unknown additional body contributing to the observed broadband photometry and excludes the SED. Ultimately, we find that the models that include the SED are a poor fit to the available data, so we adopt the system parameters derived without it. We also highlight a single transit-like event observed by TESS, deemed likely to be an eclipsing binary bound to KELT-24, that will require follow-up observations to confirm. We discuss the potential of these additional bodies in the KELT-24 system as a possible explanation for the discrepancies between the results of the different modeling approaches, and explore the system for longer-period planets that may be weakly evident in the RV observations. The comprehensive investigations that we present not only increase the fidelity of our understanding of the KELT-24 system but also serve as a blueprint for future stellar modeling in global analyses of exoplanet systems.

Keywords: Stellar properties, Multiple stars, Exoplanet systems
Assessing Exoplanetary System Architectures with DYNAMITE Including Observational Upper Limits. The information gathered from observing planetary systems is not limited to the discovery of planets, but also includes the observational upper limits constraining the presence of any additional planets. Incorporating these upper limits into statistical analyses of individual systems can significantly improve our ability to find hidden planets in these systems by narrowing the parameter space in which to search. Here, I include radial velocity (RV), transit, and transit timing variation (TTV) upper limits on additional planets in known multiplanet systems into the DYNAMITE software package and test their impact on the predicted planets for these systems. The tests are run on systems with previous DYNAMITE analysis and with updated known planet parameters in the 2–3 yr since the original predictions. I find that the RV limits provide the strongest constraints on additional planets, lowering the likelihood of finding them within orbital periods of ∼10–100 days in the inner planetary systems, as well as truncating the likely planet size (radius and/or mass) distributions toward planets smaller than those currently observed. Transit and TTV limits also provide information on the size and inclination distributions of both the known and predicted planets in the system. Utilizing these limits on a wider range of systems in the near future will help determine which systems might be able to host temperate terrestrial planets and contribute to the search for extraterrestrial biosignatures.

Keywords: Exoplanets, Astrostatistics
Probe the Regolith Characteristics of Asteroids from 9 yr Infrared Observations of WISE/NEOWISE: A Case Study of The Main-belt Object (656) Beagle. This work presents the data processing, fitting procedure, modeling, and analyzing of 9 yr infrared light curves provided by the WISE/NEOWISE telescope, by which the regolith characteristics of Main-belt Object (656) Beagle is studied. Beagle locates in the Themis family, and was proposed to be the parent of the first main-belt comet (MBC) 133P. We determine Beagle's effective diameter km, geometric albedo , mean roughness θ RMS = 44 ± 4°, mean grain size , mean specific heat capacity c p = 173 ∼ 516 J Kg‑1 K‑1, mean thermal conductivity κ = 0.7 ∼ 1.3 × 10‑3 W m‑1 K‑1, and mean thermal inertia Γ = 14 ∼ 32 J m‑2 s‑0.5 K‑1. The albedo of Beagle is a little anomalous that the albedos of Beagle's neighboring asteroids are more close to (24) Themis, rather than Beagle itself. The W1-band near-infrared (NIR) light curves do not reveal significant heterogeneous NIR features on the surface of Beagle, being inconsistent with the expectation of a family parent that has members with diverse NIR spectral types. These results add new clues of Beagle probably being an interloper or a sister, rather than the parent of its neighboring asteroids including the famous MBC 133P, hence may lead to new scenarios about the origin of 133P. Besides, we found that asteroidal shape models from inversion of optical light curves are imperfect for modeling infrared lightcurves, thus could mislead evaluations of both the heterogeneity of regolith reflectivity at NIR and thermophysical characteristics at thermal infrared.

Keywords: Small Solar System bodies, Light curves, Main belt asteroids, Infrared photometry, Asteroid surfaces
TESS Light Curves of Cataclysmic Variables. V. Improved or Corrected Orbital Periods of 53 Systems. The long and continuous high-time-resolution coverage of many stars by the Kepler and TESS space missions permit to explore periodic phenomena with a much higher precision than is possible with terrestrial observations. This includes the most basic property of binary stars, namely the orbital period. Here, I use TESS and Kepler light curves, sometimes in connection with other archival data and information taken from the literature, to improve or to correct the orbital periods of 53 cataclysmic variables with previously known periods. For 13 and 26 objects a significant or an incremental improvement, respectively, could be achieved. The periods of two systems that in the past had been only inferred indirectly were measured directly for the first time. In a remarkable 23% (12 stars) of all investigated systems previously reported orbital periods are shown to be wrong and require correction. Other interesting features seen in the light curves of some of the cataclysmic variables are briefly mentioned, but a more detailed investigation is postponed to future work.

Keywords: Close binary stars, Nova-like variable stars, Cataclysmic variable stars
Submillimeter and Mid-Infrared Variability of Young Stellar Objects in the M17SWex Intermediate-mass Star-forming Region. We present a comprehensive analysis of young stellar object (YSO) variability within the M17 Southwest Extension (M17 SWex), using 3.5 yr of monitoring data from the James Clerk Maxwell Telescope (JCMT) Transient Survey at submillimeter and 9 yr from the NEOWISE mission at mid-infrared (mid-IR). Our study encompasses observations of 147 bright submillimeter peaks identified within our deep JCMT coadded map as well as 156 YSOs in NEOWISE W1 and 179 in W2 that were previously identified in Spitzer surveys. We find three robust submillimeter variables: two are candidate YSOs and one is a likely extragalactic source. At mid-IR wavelengths, our analysis reveals secular and stochastic variability in 47 YSOs, with the highest fraction of secular variability occurring at the earliest evolutionary stage. This is similar to what has previously been observed for low-mass YSO variability within the Gould Belt. However, we observe less overall variability in M17 SWex at both the submillimeter and mid-IR. We suspect that this lower fraction is due to the greater distance to M17 SWex. Our findings showcase the utility of multiwavelength observations to better capture the complex variability phenomena inherent to star formation processes and demonstrate the importance of years-long monitoring of a diverse selection of star-forming environments.

Keywords: Submillimeter astronomy, Star forming regions, Infrared astronomy, Young stellar objects, Pre-main sequence stars, Star formation, Variable stars, Protostars
JWST-TST DREAMS: Nonuniform Dayside Emission for WASP-17b from MIRI/LRS. We present the first spectroscopic characterization of the dayside atmosphere of WASP-17b in the mid-infrared using a single JWST MIRI/LRS eclipse observation. From forward-model fits to the 5–12 μm emission spectrum, we tightly constrain the heat redistribution factor of WASP-17b to be 0.92 ± 0.02 at the pressures probed by this data, indicative of inefficient global heat redistribution. We also marginally detect a supersolar abundance of water, consistent with previous findings for WASP-17b, but note our weak constraints on this parameter. These results reflect the thermodynamically rich but chemically poor information content of MIRI/LRS emission data for high-temperature hot Jupiters. Using the eclipse mapping method, which utilizes the signals that the spatial emission profile of an exoplanet imprints on the eclipse light curve during ingress/egress due to its partial occultation by the host star, we also construct the first eclipse map of WASP-17b, allowing us to diagnose its multidimensional atmospheric dynamics for the first time. We find a day–night temperature contrast of order 1000 K at the pressures probed by this data, consistent with our derived heat redistribution factor, along with an eastward longitudinal hotspot offset of , indicative of the presence of an equatorial jet induced by day–night thermal forcing being the dominant redistributor of heat from the substellar point. These dynamics are consistent with general circulation model predictions for WASP-17b. This work is part of a series of studies by the JWST Telescope Scientist Team, in which we use Guaranteed Time Observations to perform Deep Reconnaissance of Exoplanet Atmospheres through Multi-instrument Spectroscopy.

Keywords: Exoplanet atmospheres, Exoplanet atmospheric structure