Sazuna/UAT_keywords huggingface dataset:
Neural Posterior Estimation for Cataloging Astronomical Images from the Legacy Survey of Space and Time. The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will commence full-scale operations in 2026, yielding an unprecedented volume of astronomical images. Constructing an astronomical catalog, a table of imaged stars, galaxies, and their properties, is a fundamental step in most scientific workflows based on astronomical image data. Traditional deterministic cataloging methods lack statistical coherence, as cataloging is an ill-posed problem, while existing probabilistic approaches suffer from computational inefficiency, inaccuracy, or the inability to perform inference with multiband coadded images, the primary output format for LSST images. In this article, we explore a recently developed Bayesian inference method, neural posterior estimation (NPE), for astronomical cataloging. NPE leverages deep learning to achieve both computational efficiency and high accuracy. When evaluated on the DC2 Simulated Sky Survey—a highly realistic synthetic dataset designed to mimic LSST data—NPE systematically outperforms the standard LSST pipeline in light source detection, flux measurement, star/galaxy classification, and galaxy shape measurement. Additionally, NPE provides well-calibrated posterior approximations. These promising results, obtained using simulated data, illustrate the potential of NPE in the absence of model misspecification. Although some degree of model misspecification is inevitable when applying NPE to real LSST images, several strategies can mitigate its effects.

Keywords: Astronomy image processing
Oxygen Isotope Constraints on the Importance of Photochemical Processing in Protoplanetary Disks. Observations have revealed evidence of photochemical processing in protoplanetary disks. This processing occurs in the photon-dominated layer, the optically thin regions of the disk high above the disk midplane. It remains unclear, however, how much this photochemical processing impacts the compositions of the planets and their building blocks within the disk. Here we use the oxygen isotopic compositions of solar system solids, which have been attributed to photochemistry in the solar nebula, to quantitatively evaluate whether this processing could have produced the conditions needed to provide the diversity of compositions seen in the solar system. We do this by modeling the chemical evolution while fine dust grows into the building blocks of the planets. We find that the oxygen isotopic evolution cannot be attributed to processing in the solar nebula and must instead be inherited from the parent molecular cloud. Further, our results indicate that the observed photochemical processing in protoplanetary disks does not significantly impact the compositions of planets that form within them.

Keywords: Solar nebulae, Cosmochemistry, Astrochemistry, Protoplanetary disks, Meteorites, Planet formation
Improving Generalization and Uncertainty Quantification of Photometric Redshift Models. Accurate redshift estimates are a vital component in understanding galaxy evolution and precision cosmology. In this paper, we explore approaches to increase the applicability of machine learning models for photometric redshift estimation on a broader range of galaxy types. Typical models are trained with ground-truth redshifts from spectroscopy. We test the utility and effectiveness of two approaches for combining spectroscopic redshifts and redshifts derived from multiband (∼35 filters) photometry, which sample different types of galaxies compared to spectroscopic surveys. The two approaches are (1) training on a composite dataset, and (2) transfer learning from one dataset to another. We compile photometric redshifts from the COSMOS2020 catalog (TransferZ) to complement an established spectroscopic redshift dataset (GalaxiesML). We used two architectures, deterministic neural networks (NN) and Bayesian neural networks (BNN), to examine and evaluate their performance with respect to the Legacy Survey of Space and Time (LSST) photo-z science requirements. We also use split conformal prediction for calibrating uncertainty estimates and producing prediction intervals for the BNN and NN, respectively. We find that a NN trained on a composite dataset predicts photo-z's 4.5 times less biased within the redshift range 0.3 &lt; z &lt; 1.5, 1.1 times less scattered, and has a 1.4 times lower outlier rate than a model trained on only spectroscopic ground truths. We also find that BNNs produce reliable uncertainty estimates, but are sensitive to the different ground truths. This investigation leverages different sources of ground truths to develop models that can accurately predict photo-z's for a broader galaxy population, which is crucial for surveys such as Euclid and LSST.

Keywords: Galaxy distances, Neural networks, Astronomy data analysis, Redshift surveys, Astronomical methods
The Orbital Eccentricity─Radius Relation for Planets Orbiting M Dwarfs. The orbital eccentricity─radius relation for small planets is indicative of the predominant dynamical sculpting processes during late-stage orbital evolution. Previous studies have shown that planets orbiting Sun-like stars exhibit an eccentricity─radius trend such that larger planets have higher orbital eccentricities, and that radius gap planets may have modestly higher orbital eccentricities than planets on either side of the radius gap. In this work, we investigate the trend for a sample of smaller M dwarf stars. For a sample of 236 single- and multitransit confirmed planets or candidates discovered by the TESS and Kepler missions, we constrain orbital eccentricity for each planet from the transit photometry together with a stellar density prior. We investigate the binned eccentricity─planet radius relation for the combined planet sample and present evidence for a positive eccentricity─radius relationship with elevated eccentricities for planets larger than 3.5 R⊕, similar to the trend for planets orbiting Sun-like stars. We find modest evidence that single-transit M dwarf planets near the radius gap exhibit higher eccentricity, consistent with trends for Sun-like stars. However, we see no evidence for an increased eccentricity near the radius gap among multitransit M dwarf planets. We discuss implications for these results in the context of predominant atmospheric loss mechanisms: namely, supporting evidence for photoevaporation in M dwarf planets versus planet─planet collisions or giant impacts in FGK dwarf planets.

Keywords: M dwarf stars, Transits, Exoplanets, Exoplanet dynamics
Identifying and Characterizing Very Low-mass Spectral Blend Binaries with Machine Learning Methods. We present an approach to identifying and characterizing unresolved, very low mass spectral blend binaries composed of late M, L, and T dwarfs using machine learning methodologies. We generated and evaluated a series of hierarchical random forest models to distinguish spectral blends from single very low-mass dwarfs, and to classify their primary and secondary components. Models were trained on a sample of single and synthesized binary templates generated from empirical spectra. We explored various aspects of the design of our models and found that models trained on a full range of single and binary combinations have the best performance for identification and component classification. These models achieve binary identification recall and precision of ≳85%, median component classification errors of ≲ 0.1 subtypes, and systematic classification uncertainties of ≲ 1 subtype, outperforming index-based methods in terms of fidelity, range, and speed. Optimal performance is achieved for binaries composed of L and T dwarf primaries and late L and T dwarf secondaries. When applied to the spectra of previously confirmed very low-mass binaries, model performance is degraded due to the prevalence of systems with similar component types, but remains high in the optimal performance range. We propose potential improvements to these models, which can be used to explore binary populations among the thousands to millions of very low-mass stars and brown dwarfs anticipated with large-scale spectral surveys such as SPHEREx and Euclid.

Keywords: M dwarf stars, Binary stars, L dwarfs, Random Forests, T dwarfs
KIC 9656397: Long-period, Extremely Short-eclipse Detached Eclipsing Binary with Pulsation?. We conducted a detailed study of the 700 day light curve of KIC 9656397. The target is a long-period detached eclipsing binary, exhibiting short eclipses and out-of-eclipse variations, and is reported to be a member of the open star cluster NGC 6811. We retrieved the light curve and spectra from the Kepler and LAMOST databases. We used PHOEBE to simulate the light curve and employ EMCEE to find the best-fitting physical parameters. The effective temperatures of the primary and secondary components are  Tp=6270−130+140  K and  Ts=6360−130+140  K, respectively. The mass ratio, orbital inclination, and eccentricity are  1.00−0.10+0.10 ,  89.840−0.001+0.001  deg, and  0.223−0.002+0.001 , respectively. We also derived absolute masses, radii, and luminosities of the two components, which are:  Mp=1.15−0.09+0.15  M⊙,  Ms=1.16−0.14+0.19  M⊙,  Rp=1.09−0.16+0.16  R⊙,  Rs=1.09−0.15+0.16  R⊙,  Lp=1.66−0.49+0.51  L⊙,  Ls=1.76−0.51+0.54  L⊙. We compared these values with previous results, finding a good consistency. We employed the Generalized Lomb─Scargle (GLS) method for frequency analysis and suggested that the out-of-eclipse variability is unlikely to be caused by pulsation but rather by stellar surface spots. We fitted the periodogram with Lorentzian profiles and calculated the rotation periods of two components to be 7.464 days and 6.557 days. Using the empirical formula of gyrochronology and isochrone fitting, we estimated the ages of the individual stars. Combined with LAMOST low-resolution spectra ( logg ≍4.4, [Fe/H] ≍ −0.1), the well-established age and metallicity of NGC 6811, and unpublished radial-velocity measurements, our analysis indicates that both stars are main-sequence objects with slightly subsolar metallicity and are genuine members of NGC 6811.

Keywords: Fundamental parameters of stars, Stellar physics, Detached binary stars, Eclipsing binary stars, Stellar rotation
The MUSCLES Extension for Atmospheric Transmission Spectroscopy: Spectral Energy Distributions for 20 Exoplanet Host Stars that JWST Observed in Cycle 1. Correctly interpreting JWST spectra of close-in exoplanets requires a measurement of the X-ray and ultraviolet light that the planets receive from their host stars. Here, we provide spectral energy distributions (SEDs) covering the range ≍5─1 × 107 Å for 20 transiting exoplanet host stars observed in JWST Cycle 1. The SEDs are constructed out of new and archival Hubble Space Telescope, Chandra X-ray Observatory, and/or XMM-Newton data combined with spectra from models or stars with similar properties (proxies) filling in unobserved gaps. We have also constructed SEDs of likely Habitable Worlds Observatory targets κ1 Ceti, τ Ceti, ϵ Indi, and 70 Oph B for use as proxies. We find that the JWST target planets almost all experience much stronger ultraviolet fluxes than the Earth, especially in the extreme ultraviolet, even for planets with similar overall instellation. Strong ongoing or past atmospheric escape is possible for a majority of these planets. We also assess the now considerable sample of panchromatic stellar SEDs and its applicability for current JWST observations and beyond.

Keywords: M dwarf stars, X-ray astronomy, Exoplanets, G dwarf stars, Ultraviolet astronomy, F dwarf stars, K dwarf stars, Exoplanet atmospheres
Predicting the Detection Yields of Giant Planets and Brown Dwarfs with CSST Astrometry. Chinese Space Station Telescope (CSST), which will begin its scientific operations around 2027, is going to survey the sky area of the median-to-high Galactic latitude and median-to-high ecliptic latitude. The high astrometric precision of the CSST Survey Camera for faint objects enables the detection of a number of giant planets and brown dwarfs around M dwarfs and brown dwarfs via differential astrometry in its optical survey. In this paper, we predict the number of giant planets and brown dwarfs around stars and brown dwarfs detectable with CSST astrometry. We generate synthetic samples of CSST stellar and substellar sources, and carry out companion injection-recovery simulations in the samples using different occurrence rates for FGK dwarfs, M dwarfs, and brown dwarfs. We calculate companion yields based on CSST astrometric precision. Our analysis reveals that over its 10 yr mission, the CSST Survey Camera could barely discover giant planets and low-mass BDs around FGK dwarfs, but is projected to detect 20−170 giant planets and low-mass brown dwarfs around M dwarfs within 300 pc, and 300−570 brown dwarf binaries within 600 pc. Therefore, CSST astrometry is likely to significantly increase the current sample of substellar companions around M dwarfs and brown dwarfs. This sample will deepen our understanding of planet formation and evolution around low-mass stars and brown dwarfs.

Keywords: Brown dwarfs, Astrometric exoplanet detection, Exoplanet astronomy, Low mass stars, Space astrometry, Space telescopes
A High-resolution Near-Ultraviolet Transmission Spectrum of KELT-9b: Mg II and Fe II Escaping from the Hottest Known Giant Planet. We present high-resolution near-ultraviolet observations from the Hubble Space Telescope's Space Telescope Imaging Spectrograph (STIS) data for the hottest known gas planet, KELT-9b. Observations were collected with STIS/E230M (2300─3000 Å, R ∼ 30,000), and we decorrelate systematic effects from the telescope using jitter detrending. We show the clear presence of the Mg II doublet at 2800 Å and Fe II at 2600 Å in KELT-9b. The Mg II is measured above the planet's Roche transit radius, indicating it is escaping. We fit 1D non─local thermodynamic equilibrium (NLTE) atmospheric escape models to these features, demonstrating a significant loss of mass in KELT-9b's atmosphere ( Ṁ≍1012  g s−1); we also find a remarkably high line-broadening corresponding to a velocity of about 50─75 km s−1, and a net blueshift of the Mg II doublet greater than 30 km s−1. Future 3D MHD modeling of the spectrum and gas kinematics is likely needed to explain these observations. We interpret these results in the context of the Mg II "Cosmic Shoreline" and show that the detection of escaping Mg II in KELT-9b and the nondetection in WASP-178b are consistent with the hypothesis that stars hotter than Teff ∼ 8250 K have relatively low levels of X-ray and extreme ultraviolet (XUV) radiation due to the lack of a chromosphere. Therefore, planets around such early-type stars experience a different degree of atmospheric escape. This result highlights the importance of XUV irradiation in driving atmospheric escape inside and outside the solar system.

Keywords: Hot Jupiters, Exoplanet atmospheric dynamics, Ultraviolet spectroscopy, Transmission spectroscopy, Exoplanet atmospheres, Exoplanet atmospheric evolution
RV×TESS. I. Modeling Asteroseismic Signals with Simultaneous Photometry and Radial Velocities. Detecting small planets via the radial velocity (RV) method remains challenged by signals induced by stellar variability, versus the effects of the planet(s). Here, we explore using Gaussian process (GP) regression with Transiting Exoplanet Survey Satellite (TESS) photometry in modeling RVs to help to mitigate stellar jitter from oscillations and granulation for exoplanet detection. We applied GP regression to simultaneous TESS photometric and RV data of HD 5562, a G-type subgiant (M⋆ = 1.09M⊙, R⋆ = 1.88R⊙) with a V magnitude of 7.17, using photometry to inform the priors for RV fitting. The RV data is obtained by the Magellan Planet Finder Spectrograph. The photometry-informed GP regression reduced the RV scatter of HD 5562 from 2.03 to 0.51 m s−1. We performed injection and recovery tests to evaluate the potential of GPs for discovering small exoplanets around evolved stars, which demonstrate that the GP provides comparable noise reduction to the binning method. We also found that the necessity of photometric data depends on the quality of the RV dataset. For long baseline and high-cadence RV observations, GP regression can effectively mitigate stellar jitter without photometric data. However, for intermittent RV observations, incorporating photometric data improves GP fitting and enhances detection capabilities. *This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: Exoplanet astronomy, Stellar oscillations, Asteroseismology, Radial velocity
Red Noise─based False Alarm Thresholds for Astrophysical Periodograms via Whittle's Approximation to the Likelihood. Astronomers who search for periodic signals using Lomb─Scargle periodograms rely on false alarm level (FAL) estimates to identify statistically significant peaks. Although FALs are often calculated from white noise models, many astronomical time series suffer from red noise. Prewhitening is a statistical technique in which a continuum model is subtracted from the log power spectrum estimate, after which the observer can proceed with a white-noise treatment. Here we present a prewhitening-based method of calculating frequency-dependent FALs. We fit power laws and autoregressive models of order 1 to each Lomb─Scargle periodogram by minimizing the Whittle approximation to the negative log-likelihood (NLL), then calculate FALs based on the best-fit model power spectrum. Our technique is a novel extension of the Whittle NLL to datasets with uneven time sampling. We demonstrate FAL calculations using observations of α Cen B, GJ 581, HD 192310, synthetic data from the radial velocity (RV) fitting challenge, and Kepler observations of a differential rotator. The Kepler data analysis shows that only true rotation signals are detected by red noise FALs, while white noise FALs suggest all spurious peaks in the low-frequency range are significant. A high-frequency sinusoid injected into α Cen B  logR'HK  observations exceeds the 1% red noise FAL despite having only 8.9% of the power of the dominant rotation signal. In a periodogram of HD 192310 RVs, peaks associated with differential rotation and planets are detected against the 5% red noise FAL without iterative model fitting or subtraction. The software for calculating red noise─based FALs is available on GitHub.

Keywords: Exoplanet detection methods, Lomb-Scargle periodogram, Astrostatistics, Period search , Radial velocity, Red noise, Time series analysis
First Light for the New 30 m Parabolic Radio Telescope at ArQi: Implications for Space Weather Monitoring. Interplanetary scintillation (IPS) phenomenon behaves as twinkling of a compact radio source due to scattering in the solar wind. Here we report the first identification of IPS signal by a new parabolic dish antenna with its diameter of 30 m, observed on 2024 March 1. The radio source of 3C446 at solar elongation of 6.4° was targeted during its 5 minute transit across our antenna beam at ArQi (115.13°E, 44.73°N). Our receiver is characterized as simultaneous measurements of dual polarizations from 3C446 emission, integrated over a 40 MHz bandwidth around its central frequency of 1.4 GHz. The horizontally and vertically polarized components, though independently and simultaneously measured, show a strong correlation in terms of both time-series and power spectral analyses. Using a spectra-fitting method on basis of the classic IPS theory, the solar wind speed in our observation case is inferred to be 283 km s−1. Such a solar wind speed inferred at the piercing point of 24 solar radii along our IPS ray-path reaffirms the interplanetary diagnostic capability of ground-based IPS technique. Our first-light IPS observation at ArQi represents a significant advance in the ongoing commissioning phase of our IPS-dedicated telescope facility within the Chinese Meridian Project─Phase II.

Keywords: Interplanetary scintillation, Space weather, Solar wind, Radio telescopes, Radio sources
A Near-Earth Object Model Calibrated to Earth Impactors. The population of Earth-impacting meteoroids and their size-dependent orbital elements are key to understanding the origin of meteorites and informing planetary defense efforts. Outstanding questions include the role of collisions in depleting meteoroids on highly evolved orbits and the relative importance of delivery resonances. Those depend on size, with current dynamical models considering only asteroids larger than 10 m in diameter. Based on 1202 sporadic meteoroids observed by the Global Fireball Observatory, we created a debiased model of the near-Earth meteoroid population in the 10 g─150 kg size range (approximately 1 cm─0.5 m in diameter) as they dynamically evolved from the main asteroid belt onto Earth-crossing orbits. The observed impact population is best matched with a collisional half-life decreasing from 3 Myr for meteoroids of 0.6 kg (7 cm) or higher to 1 Myr below this size, extending to the model lower bound of 10 g. Placing our results in context with near-Earth object models for larger sizes, we find that the inner main belt continues to dominate feeding the small 1─10 m diameter population primarily via the ν6 secular resonance and the 3:1J mean-motion resonance. We also evaluated the potential significance of physical processes other than collisions on Earth-impacting meteoroids, such as low-perihelion disruptions from thermal stresses.

Keywords: Near-Earth objects, Fireballs
Tracing Galaxy Evolution in the Nearby Universe: The Role of Dark Matter. Using a sample of ∼126,000 late-type galaxies (LTGs) from the Sloan Digital Sky Survey, we analyzed stellar mass as a function of the dynamical mass. Stellar masses are estimated using eight stellar population synthesis (SPS) models with constant initial mass functions (IMFs), while dynamical masses are derived from seven formulations based on Newtonian dynamics and virial equilibrium, incorporating both stellar and gas velocity dispersions. We account for key factors affecting dynamical mass estimation, including the inclination, colour, concentration, and Sérsic index. We find that the difference between dynamical and stellar mass ( ∆logM ) ranges from nearly zero to ∼95% of the dynamical mass, depending on mass and redshift.  ∆logM  appears to decrease with increasing redshift, but exhibits a saddlelike shape at low mass and low redshift—especially in disk-dominated LTGs—transitioning into a steep, linear trend at higher masses and redshifts. In the high-mass regime, the behavior resembles that of early-type galaxies. Moreover, our results indicate that this evolution is not discrete but follows a continuous transition between morphological regimes. Dark matter within LTGs is at most equal to  ∆logM , depending on the impact of the IMF and SPS on stellar mass estimation. Although SPS-based stellar masses do not include the gas component, previous studies have shown that galaxies with log(MStellar/MSolar) &gt; 10 at z ≤ 0.3 are predominantly stellar-mass dominated. Most galaxies in our sample fall within this regime, minimizing the impact of gas exclusion. Our findings go beyond the scope of individual galaxies, providing insight into the nearby Universe and highlighting the role of dark matter in determining galaxies' structure and evolution.

Keywords: Cosmology, Galaxy distances, Late-type galaxies, Galaxy photometry, Dark matter