Sazuna/UAT_keywords huggingface dataset:
A Comprehensive Analysis of Rovibrational CO in the Era of JWST. We present an analysis of CO rovibrational emission lines in the 183 infrared spectra of nearby Class II objects obtained with the NIRSPEC instrument on the Keck II telescope over the past two decades. The sample includes a broad range of stellar mass (both T Tauri and Herbig Ae/Be) and disk evolutionary states (from full to debris disks). We find that 53% of the sample has CO rovibrational emission lines present in their spectrum with disk/stellar subtype detection rates of 82% for transition disks, 61% for Herbigs, and 77% for classical T Tauri stars. Although there is no discernible difference between T Tauri and Herbig Ae/Be star CO detection rates, the detection of accretion and of CO are statistically correlated in T Tauri stars but not in Herbig Ae/Be objects. Within the sample of T Tauri stars, we find that no weak-line T Tauri stars have CO rovibrational emission lines. We use slab modeling to analyze the density, temperature, and emitting area of the sample. The retrieval results imply that Herbig Ae/Be objects tend to have cooler and larger CO emitting regions than T Tauri stars. We find that the CO emitting area is not a thin ring as defined by temperature, but a ring of varying size, likely dependent on the structure of the disk. We also present guidelines on how to approach CO rovibrational emission lines in JWST spectra and present methods for linking ground-based observations with JWST spectra. This includes line-to-continuum ratio estimates based on stellar mass and accretion rate.

Keywords: Infrared spectroscopy, Protoplanetary disks, Planet formation, CO line emission
A 16 Myr Super-Neptune in Upper Centaurus Lupus and a Preliminary Survey of Transiting Planets in Sco-Cen with TESS. Measuring the properties of planets younger than about 50 Myr helps to test different planetary formation and evolution models. NASA's Transiting Exoplanet Survey Satellite (TESS) has observed nearly the entire sky, including a wide range of star-forming regions and young stellar clusters, expanding our census of the newborn planet population. In this work, we present the discovery of the TIC 88785435 planetary system located in the Upper Centaurus Lupus (UCL) region of the Scorpius Centaurus OB association (Sco-Cen) and a preliminary survey of the planet population within Sco-Cen. TIC 88785435 is a pre-main-sequence, K7V dwarf (M⋆ = 0.72 M⊙, R⋆ = 0.91 R⊙, Teff = 3998 K, V = 11.7 mag) located within the bounds of UCL. We investigate the distribution of rotation periods measured from the TESS long-cadence data and the Hα and Li abundances from the spectra of TIC 88785435. TESS long-cadence data reveal that TIC 88785435 hosts a transiting super-Neptune (Rb = 5.03 R⊕, P = 10.51 days), TIC 88785435b. Ground-based follow-up validates the planetary nature of TIC 88785435b. Using the TESS data, we perform a preliminary survey to investigate how TIC 88785435b compares to the population of newly born planets located within Sco-Cen.

Keywords: Exoplanet astronomy, Young star clusters, Exoplanets
Microlensing Constraints on the Stellar and Planetary Mass Functions. The mass function (MF) of isolated objects measured by microlensing consists of both a stellar and a planetary component. We compare the microlensing MFs of A. Gould et al. and T. Sumi et al. to other measurements of the MF. The abundance of brown dwarfs from the tail of the T. Sumi et al. stellar MF is consistent with measurements from the local solar neighborhood. Microlensing free-floating planets (μFFPs) may be free-floating or orbit host stars with semimajor axes a ≳ 10 au and therefore can constrain the populations of both free-floating and wide-orbit planets. Comparisons to radial velocity and direct imaging low-mass companion populations suggest that either most of the μFFP population with masses &gt; 1 MJup is bound to hosts more massive than M dwarfs, or some fraction of the observed companion population 1 MJup &lt; mp &lt; 0.08 M⊙ actually comes from the low-mass tail of the stellar MF. The μFFP population also places strong constraints on planets inferred from debris disks and gaps in protoplanetary disks observed by the Atacama Large Millimeter/submillimeter Array.

Keywords: Gravitational microlensing exoplanet detection, Debris disks, Protoplanetary disks, Exoplanets
Investigating Transit Timing Variations in the Ultrashort Period Exoplanet WASP-19b. In this study, we present a comprehensive analysis of transit timing variations (TTVs) in the ultrashort-period gas giant WASP-19b, which orbits a G-type main-sequence star. Our analysis is based on a data set comprising 204 transit light curves (LCs) obtained from the Transiting Exoplanet Survey Satellite, the Exoplanet Transit Database, and the ExoClock project, supplemented by 18 publicly available LCs. Mid-transit times were extracted from these data, and an additional 98 mid-transit times compiled from the literature were incorporated, resulting in a combined data set spanning 14 yr. After excluding LCs significantly impacted by stellar activity, such as starspot anomalies, the final data set consisted of 252 high-quality mid-transit times. Initial inspection of the transit timing residuals using an apsidal precession model suggested the possible presence of an additional planetary companion. However, subsequent frequency analysis and sinusoidal model fitting indicate that the observed TTVs are more consistently explained by apsidal precession of WASP-19b's orbit. We also considered alternative mechanisms, including the Applegate mechanism and the Shklovskii effect. Our findings suggest that stellar magnetic activity, potentially linked to the Applegate mechanism, may also contribute to the observed timing variations. To further constrain the origin of the TTVs and assess the contributions of these mechanisms, continued high-precision photometric monitoring of the WASP-19 system is strongly recommended.

Keywords: Hot Jupiters, Transit timing variation method, Exoplanets
Young Stellar Objects in the Carina Nebula: Near-infrared Variability and Spectroscopy. We present a catalog of 652 young stellar objects (YSOs) in the Carina star-forming region. The catalog was constructed by combining near-infrared KS-band variability from the VISTA Variables in the Vía Láctea eXtended survey and medium-resolution H-band spectroscopy from APOGEE-2, Sloan Digital Sky Survey IV (SDSS-IV). Variability analysis of 6.35 million sources identified 606 variable stars. The classification of the spectral lines by semisupervised K-means clustering of 704 stars, refined through comparison with known catalogs in literature and visual inspection of the spectra, was performed. Combined with KS variability, the final catalog contains three groups: Emission-line YSOs, Absorption-line YSOs, and Literature/Variable-identified YSOs. Cross validation with the Gaia DR3 proper motion and distance estimates supports Carina membership for 415 sources. The statistical characterization of YSO variability demonstrated that most Carina members (78%) exhibit variability patterns. Of these, 134 stars show emissions in their spectra, which is consistent with some accretion processes. Analysis of fundamental stellar parameters from StarHorse and Gaia DR3 reveals typical distributions of YSOs, dominated by low-mass (1–4M⊙), solar-metallicity stars with temperatures between 4000 and 6000 K. Only a small fraction (4%) of the sources are more massive than 4M⊙, suggesting limited ongoing massive star formation in Carina. This well-characterized catalog also offers a robust training data set for machine learning applications aimed at predicting YSO behavior.

Keywords: Herbig Ae/Be stars, Periodic variable stars, Star forming regions, Young stellar objects, Irregular variable stars
The James Webb Space Telescope Absolute Flux Calibration. IV. Near-Infrared Imager and Slitless Spectrograph Imaging. The absolute flux calibration of the Near-infrared Imager and Slitless Spectrograph (NIRISS) imaging modes is derived using observations of photometric standards with the James Webb Space Telescope (JWST). The calibration converts the ramp slope to a mean surface brightness in MJy sr‑1, and is measured by combining aperture photometry corrected to infinite aperture with predicted mean flux densities of the stars from stellar models plus the solid angle per pixel. Photometric standards of three types (white dwarf stars, A-type stars, and solar analogs) were observed to identify possible systematic errors in the calibration. Variations in the calibration factors with time, count rate, peak pixel signal, and detector subarray were investigated. Average calibration factors have been calculated using an inverse-variance weighted mean, suitable if the values are subject to only statistical variations, and using an unweighted object-by-object mean, suitable if the values differ due to systematic effects between the stars. The two mean values indicate calibration uncertainties of 0.5%–0.9%. Standard LDS 749B, used for the commissioning calibration, is found to have values that are higher by 6%–9% compared to the mean values from the other standards in the F277W through F480M filters. This indicates an issue with the LDS 749B stellar model at these wavelengths. For some standards, there may be systematic offsets at the 1%–2% level in the longer-wavelength NIRISS filters. Cross-comparison with measurements from other JWST instruments is needed for verification of these offsets.

Keywords: Infrared astronomy, James Webb Space Telescope, Flux calibration
Discovery of Faint Nebulosity around a Z Camelopardalis–type Cataclysmic Variable in Antlia: Nova Shell or Ancient Planetary Nebula?. We report our discovery of a faint nebula surrounding a previously little-studied 15th mag variable star, ASASSN-19ds, in the Southern Hemisphere constellation Antlia. Spectra verify that the star is a cataclysmic variable (CV). Using new and archival photometry, we confirm that ASASSN-19ds is an eclipsing binary with an orbital period of 0.139 days (3.34 hr). Moreover, its out-of-eclipse brightness shows a "sawtooth" light curve with an amplitude of ∼1 mag and an interval between peaks that varies between about 3 to nearly 5 weeks. Its mean absolute magnitude in the Gaia system is MG = +6.5. These combined properties lead to a classification of ASASSN-19ds as a Z Camelopardalis–type CV. We obtained deep narrowband images of the nebulosity, using modest-sized telescopes and extremely long exposure times. Our imagery reveals a bipolar morphology, with thin arcs at the ends of the major axis, likely indicating an interaction with the interstellar medium. We consider several scenarios for the origin of the nebula, but from the existing information we are unable to distinguish between it being ejecta from an unobserved classical-nova outburst several centuries ago, or an ancient planetary nebula. Future observations should be able to decide between these possibilities. At the star's distance of only ∼557 pc, a nova eruption would have been a spectacular naked-eye event.

Keywords: Dwarf novae, Planetary nebulae nuclei, Planetary nebulae, Emission nebulae, Z Camelopardalis stars, Nova-like variable stars, Cataclysmic variable stars
Distributions of Wide Binary Stars in Theory and in Gaia Data. II. Reconstruction of Sample Probability Density of True Orbit Sizes. Wide binary stars are important for testing alternative models of gravitation in the weak-field regime and understanding the statistical outcomes of dynamical interactions in the general Galactic field. The Gaia mission's collection of weakly bound pairs of stars offers a unique opportunity to estimate the rate of survivors at separations above 7 KAU, where non-Newtonian components of gravitation may become important. The available Gaia-based catalogs of resolved binaries provide the projected angular separation between the components, while the physical semimajor axis is the parameter of interest. The problem of reconstructing the distribution of orbit sizes is complex and ill-posed, because the observed apparent separations are defined by a number of underlying physical parameters including semimajor axis, eccentricity, orbit orientation, and orbital phase. Methods of inverse reconstruction of the marginal distribution of semimajor axes from the available data are proposed and implemented with two different strategies, namely, a direct Monte Carlo mapping and inverse filtering with impulse updates without regularization. We find rather similar results from the two methods for the outlying tail of the distribution, suggesting that the rate of orbit sizes is a shallow declining function on a logarithmic scale. A finite rate of extremely wide binaries is implied.

Keywords: Orbital elements, Monte Carlo methods, Semimajor axis, Astrostatistics techniques, Astrostatistics distributions, Wide binary stars, Gaia
An Efficient Method for Measuring the Color of a Natural Satellite with Astrometric Applications. The Gaia DR3 catalog released in 2022 contains precise broadband photometry for more than one billion stars in the G, BP, and RP passbands, which is very useful for calibrating the differential color refraction (DCR) effect in ground-based observations. It is a pity, however, that the catalog does not provide color indices (e.g., BP ‑ RP) for Solar System Objects, such as natural satellites. In this study, we try to measure the Gaia standard color of a natural satellite by transforming the instrumental color index to a Gaia standard one using a local Johnson–Cousins photometric system (BVRI). This method requires only a few CCD frames and a few reference stars in each frame. To verify its effectiveness and applicability, we measured the colors of three natural satellites: Himalia (JVI), Phoebe (SIX), and Triton (NI). We found that the results are quite good, with a measurement uncertainty that can be less than 0.01 mag. Based on the measured color indices, we corrected the DCR effect in our observations, significantly improving astrometric accuracy and precision. For example, the standard deviations of the positional (O ‑ C) residuals (observed minus computed) for Himalia improved from 0 .″ 084 to 0 .″ 021 in R.A., and for Phoebe, from 0 .″ 031 to 0 .″ 012.

Keywords: Johnson photometry, Natural satellites (Solar system), Atmospheric refraction, Astrometry, Astronomy image processing
Meteoroid Stream Identification with HDBSCAN Unsupervised Clustering Algorithm. Accurate identification of meteoroid streams is central to understanding their origins and evolution. However, overlapping clusters and background noise hinder classification, an issue amplified for missions such as the European Space Agency's Lunar Meteoroid Impact Observer that rely on meteor shower observations to infer lunar meteoroid impact parameters. This study evaluates the performance of the Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN) algorithm for unsupervised meteoroid stream identification, comparing its outcomes with the established Cameras for All-Sky Meteor Surveillance (CAMS) look-up table method. We analyze the CAMS Meteoroid Orbit Database v3.0 using three feature vectors: LUTAB (CAMS geocentric parameters), ORBIT (heliocentric orbital elements), and GEO (adapted geocentric parameters). HDBSCAN is applied with varying minimum cluster sizes and two cluster selection methods (eom and leaf). To align HDBSCAN clusters with CAMS classifications, the Hungarian algorithm determines the optimal mapping. Clustering performance is assessed via the Silhouette score, Normalized Mutual Information, and F1 score, with Principal Component Analysis further supporting the analysis. With the GEO vector, HDBSCAN confirms 39 meteoroid streams, 21 strongly aligning with CAMS. The ORBIT vector identifies 30 streams, 13 with high matching scores. Less active showers pose identification challenges. The eom method consistently yields superior performance and agreement with CAMS. Although HDBSCAN requires careful selection of the minimum cluster size, it delivers robust, internally consistent clusters and outperforms the look-up table method in statistical coherence. These results underscore HDBSCAN's potential as a mathematically consistent alternative for meteoroid stream identification, although further validation is needed to assess physical validity.

Keywords: Classification, Meteoroids, Meteor streams, Meteor showers, Meteors
Investigating the Binary Source Degeneracy for Wide-orbit Planets. Wide-orbit planets are particularly sensitive to detection by the Roman Galactic Bulge Time Domain Survey (GBTDS). This study investigates the degeneracy of these events with binary sources, focusing on how observation cadence affects the resolution of these degeneracies. We analyzed the impact of various cadences from  (3.6minutes)‑1  to (5 hr)‑1, which encompasses planned cadences for both the GBTDS and cadences used by ground-based surveys like KMTNet. The results show that a  ∼(15minutes)‑1  cadence is generally sufficient to resolve this degeneracy unless the source star is a giant (ρ ≳ 0.01).

Keywords: Gravitational microlensing exoplanet detection, Binary source microlensing
Down But Not Out: The Case of Long-period Comet C/2021 O3 (Panstarrs). We combine ground- and space-based observations of long-period comet C/2021 O3 (Panstarrs; perihelion distance 0.287 au) in order to investigate its reported near-perihelion destruction. Preperihelion photometric observations show a remarkably small heliocentric dependence of the scattered light,  ∝rH‑s  with s = 2.59 ± 0.21, distinct from values reported in other long-period comets, for which s = 4 is the canonical standard. The index is smaller than expected of coma production by equilibrium sublimation of either supervolatiles (for which s ∼ 4 is expected) or water ice (s ∼ 6–8) across the ∼4 to 2 au range. The absolute magnitude deduced from the preperihelion data is H = 13.0 ± 0.3 (coma scattering cross section ∼225 km2 for an assumed geometric albedo 0.04), while after perihelion the cross section fades by a factor of 25 to H = 16.5 (∼9 km2). STEREO spacecraft observations near perihelion show a long debris trail whose properties are consistent with forward scattering from radius ∼7 μm particles. The data show that the nucleus of C/2021 O3 was not destroyed at perihelion. Although the light curve from 3.9 au inbound to 0.8 au outbound is not uniquely determined, a simple explanation is provided by seasonal dimming on a nucleus having high obliquity and an asymmetric distribution of near-surface volatiles. The survival of the nucleus against rotational disruption suggests a preperihelion nucleus radius rn ≳ 1.0 km, while the photometric limit to the radius of the nucleus after perihelion is rn &lt; 1.7 km (geometric albedo 0.04 assumed).

Keywords: Comet nuclei, Long period comets, Comet origins, Comet volatiles , Oort cloud objects
Spectroscopic Orbits of Subsystems in Multiple Stars. XI. Adding to the large radial velocity survey of nearby solar-type stars (summary in Tokovinin, 2023a), spectroscopic orbits are determined for four hierarchical systems: HIP 49442 (inner and outer periods of 164.55 days and 34 yr, respectively), HIP 55691 (2.4 and 415 yr), HIP 61465 (86.8 days), and HIP 78662C (0.82 day). Each system is discussed individually. Seven Gaia orbits of low-mass dwarfs, each with two additional resolved (interferometric and wide) companions, i.e., potential quadruples, are tested by monitoring radial velocities: five orbits are confirmed and two are refuted. Five of these systems are quadruples of 3+1 hierarchy, one is quintuple, and one is triple. Strengths and limitations of the Gaia data on multiple systems and the need of complementary observations are highlighted.

Keywords: Spectroscopic binary stars, Multiple stars, Binary stars, Visual binary stars
How Massive Star Clusters Form and Evolve: A Near-IR Survey of the W51 Complex. We present near-infrared JHKs and narrowband H2(1─0) photometric observations of the W51A region, obtained with GTC EMIR, aiming to characterize its young stellar population, and provide mass estimates for individual cluster members and the protoclusters. Our observations reveal over 3000 new sources, out of which 88 are located in the protoclusters, W51 IRS2 and W51 Main. The average extinction (AV), measured from the J ─ H color, of sources is 19AV in W51 IRS2 and 14AV in W51 Main. We document 17 new instances of H2 emission in the region by utilizing observations from the H2(1─0) narrowband filter. Despite limited completeness, we estimated masses for each cluster member and estimated the total cluster mass to be in the range of 900─4700M⊙for W51 IRS2 and 500─2700M⊙ for W51 Main, using an assumed age range of 1─3 Myr. We measured the initial mass function (IMF) in the proto-clusters assuming a range of ages from 1─3 Myr and found that the IMF slopes for both protoclusters are consistent with the Salpeter IMF in the mass range M ≳ 8M⊙within 1σ─2σ.

Keywords: Protoclusters, Infrared photometry, Near infrared astronomy
An Hα Cloud in the H I Tail: Recent Star Formation in the Outskirts of NGC 4258 Revealed by Nanshan 1 m Telescope. We present first-light deep Hα imaging taken with the Nanshan 1 m wide-field telescope on the local galaxy NGC 4258, alongside archival data from Hubble Space telescope (HST), Westerbork Synthesis Radio Telescope, and The Dark Energy Camera Legacy Survey. The Hα image shows ongoing star formation not only inside the galaxy but also in an H I cloud in the eastern H I tail, which is roughly 16 kpc away from the main galaxy. The HST images reveal several ultrablue compact objects (F555W ‑ F814W &lt; ‑0.5 mag, FWHM ∼ 0 .″ 2) in the Hα bright region, aligned with the H I tail, suggesting the presence of young open cluster candidate in the H I tail. Our results suggest that wide field Hα imaging is a valuable tool for investigating recent star formation in the extended regions of NGC 4258. Furthermore, the star formation in diffuse H I tails could highlight an potential aspect of galaxy stellar halo formation, warranting further investigation of the impact of star formation in halos on galaxy evolution.

Keywords: Narrow band photometry
Updated Masses for the Gas Giants in the Eight-planet Kepler-90 System Via Transit-timing Variation and Radial Velocity Observations. The eight-planet Kepler-90 system exhibits the greatest multiplicity of planets found to date. All eight planets are transiting and were discovered in photometry from the NASA Kepler primary mission. The two outermost planets, g (Pg = 211 days) and h (Ph = 332 days), exhibit significant transit-timing variations (TTVs), but were only observed six and three times, respectively, by Kepler. These TTVs allow for the determination of planetary masses through dynamical modeling of the pair's gravitational interactions, but the paucity of transits allows a broad range of solutions for the masses and orbital ephemerides. To determine accurate masses and orbital parameters for planets g and h, we combined 34 radial velocities (RVs) of Kepler-90, collected over a decade, with the Kepler transit data. We jointly modeled the transit times of the outer two planets and the RV time series, then used our two-planet model to predict their future times of transit. These predictions led us to recover a transit of Kepler-90 g with ground-based observatories in 2024 May. We then combined the 2024 transit and several previously unpublished transit times of planets g and h with the Kepler photometry and RV data to update the masses and linear ephemerides of the planets, finding masses for g and h of 15.0 ± 1.3 M⊕ and 203 ± 16 M⊕, respectively, from a Markov Chain Monte Carlo analysis. These results enable further insights into the architecturally rich Kepler-90 system and pave the way for atmospheric characterization with space-based facilities.

Keywords: Radial velocity, Extrasolar gaseous planets, Exoplanets, Transit timing variation method