Sazuna/UAT_keywords huggingface dataset:
PAH Marks the Spot: Digging for Buried Clusters in Nearby Star-forming Galaxies. The joint capabilities of the Hubble Space Telescope (HST) and JWST allow for an unparalleled look at the early lives of star clusters at near- and mid-infrared wavelengths. We present here a multiband analysis of embedded young stellar clusters in 11 nearby, star-forming galaxies, using the PHANGS-JWST and PHANGS-HST data sets. We use the Zooniverse citizen science platform to conduct an initial by-eye search for embedded clusters in near-UV/optical/near-infrared images that trace stellar continuum emission, the Paschenα and Hα recombination lines, and the 3.3 μm polycyclic aromatic hydrocarbon feature and its underlying continuum. With this approach, we identify 292 embedded cluster candidates for which we characterize their ages, masses, and levels of line-of-sight extinction by comparing the photometric data to predictions from stellar population models. The embedded cluster candidates have a median age of 4.5 Myr and an average line-of-sight extinction &lt;AV&gt; = 6.0 mag. We determine lower limits on source stellar masses, resulting in a median stellar mass of 103 M⊙. We use this sample of embedded cluster candidates to train multiple convolutional neural network models to carry out deep transfer learning-based searches for embedded clusters. With the aim of optimizing models for future catalog production, we compare results for four variations of training data using two neural networks. Confusion matrices for all eight model configurations, as well as inter-model identification trends, are presented. With refinement of the training sample, we determine that optimized models could serve as a pathway for future embedded cluster identification beyond our 11 galaxy sample.

Keywords: Interstellar dust, Polycyclic aromatic hydrocarbons, Spiral galaxies, Star forming regions, Star formation, Star clusters
A Combined TESS and Ground-based Study of Transit Timing Variations in HAT-P-16, TOI-1516 and TOI-2046 Systems. We present new results for the hot Jupiters HAT-P-16b, TOI-1516b, and TOI-2046b, based on photometric observations collected using both space- and ground-based facilities. Ground-based data were collected in the 2020─2024 time span with the 0.6 m telescope (ADYU60) located at the Adiyaman University Application and Research Center (Adiyaman, Türkiye) and the 1.0 m telescope at the Türkiye National Observatory (TUG, Türkiye). Through a combination of fits to our ground-based data, the midtransit times data from TESS, and additional data taken from the literature, we present an updated linear ephemeris for each system. Transit timing variations (TTVs) were analyzed using linear, orbital decay, and apsidal precession models. The resulting BIC(∆BIC) values indicate that the orbital decay model is statistically favored for HAT-P-16b and TOI-1516b, while the constant period model is preferred for TOI-2046b. False alarm probabilities (FAPs) were computed to assess the significance of any periodic signals. TOI-1516b displays a strong TTV signal with a FAP (of 0.0001) well below the 0.01 threshold, suggesting a likely dynamical origin that warrants further investigation. The higher FAP value (0.0055) for HAT-P-16b suggests that the case of a possible presence of an additional body in the system is less convincing. In contrast, the much higher FAP value (0.0196) for TOI-2046b implies that there are no statistically significant TTVs.

Keywords: Exoplanet astronomy, Exoplanet detection methods, Transit timing variation method, Exoplanets
Toward a 2D H I Map of the Local Interstellar Medium. Obtaining a complete census of gas in the local interstellar medium (LISM; &lt;100 pc) is challenging given the limited available tracers of the warm, partially ionized medium. Medium- to high-resolution UV absorption spectroscopy toward individual nearby stars is the primary method used, and incomplete spatial sampling of this complex medium makes a global map of the material difficult. Using H I column density measurements derived from H I Lyα spectroscopy toward 164 stars inside 100 pc, we have generated 2D spatially interpolated N(H I) maps for different distance shells. Based on the area-weighted sky averages, we find that sight lines inside 10 pc typically have log10[N(H I)/cm−2] ∼ 17.9. For greater distance shells, log10[N(H I)/cm−2] increases to 18.3 (10─20 pc), then to 18.4 (20─70 pc), and finally to 18.6 (70─100 pc). This last increase is likely associated with the detection of the Local Bubble boundary, thus making the plateau of column density from 20 to 70 pc notable and suggestive of the rarity of warm LISM material beyond ∼10─20 pc. We estimate that the uncertainties associated with N(H I) values inferred from the interpolated sky maps are approximately inversely correlated with the number of samples in each distance shell, and are in the range of 0.20─0.48 dex, compared to the 0.01─0.30 dex typically determined from direct Lyα observations. We discuss the impact of these uncertainties on interstellar medium corrections of extreme-UV and Lyα observations for nearby stars. Denser spatial sampling of the sky via UV absorption spectroscopy of nearby stars is required to improve the accuracy of these N(H I) estimates.

Keywords: Interstellar absorption, Extreme ultraviolet astronomy
SPORES-HWO. II. Companion Mass Limits and Updated Planet Properties for 120 Future Exoplanet Imaging Targets from 35 yr of Precise Doppler Monitoring. A goal of the future Habitable Worlds Observatory (HWO) is to directly image and spectroscopically characterize true Earth-analogs. However, if a large fraction of HWO target stars host unknown dynamically disruptive giant planets in their habitable zones (HZs), then additional targets that are farther away will need to be surveyed, potentially requiring a larger-aperture telescope and a coronagraph with a smaller inner working angle. Therefore, the sooner we constrain the presence of massive planets orbiting potential HWO target stars, the easier and less costly it will be to adjust key aspects of HWO's architecture. In this work, we uniformly analyze over 153,000 public radial velocity (RV) observations of 120 potential HWO target stars to derive mass limits on planetary companions. The RVs were measured by 23 spectrographs located at 15 observatories around the world, with the first observations going back to 1987. Based on empirical search completeness tests, we determine that undetected Jupiter-mass (Saturn-mass) planets may be hiding in up to 38% (53%) of the HZs of targets in the ExEP Mission Star List. The median mass sensitivity limit in the middle of the conservative HZ is approximately 48 M⊕. We also provide updated parameters for 53 known companions, and we detect at least 26 additional RV signals corresponding to stellar activity and 4 signals that are planet candidates. We note that 44 of the ExEP stars lack substantial RV monitoring history, and we advocate for community-coordinated observing campaigns of these stars using moderate-precision RV facilities. ∗SPORES-HWO: System Properties and Observational Reconnaissance for Exoplanet Studies with the Habitable Worlds Observatory.

Keywords: Exoplanet astronomy, Astrobiology, Planet hosting stars, Radial velocity, Habitable planets
The CHARA Array Polarization Model and Prospects for Spectropolarimetry. Polarimetric data provide key insights into infrared emission mechanisms in the inner disks of young stellar objects (YSOs) and the details of dust formation around asymptotic giant branch (AGB) stars. While polarization measurements are well-established in radio interferometry, they remain challenging at visible and near-infrared wavelengths, due to the significant time-variable birefringence introduced by the complex optical beam train. In this study, we characterize instrumental polarization effects within the optical path of the Center for High Angular Resolution Astronomy (CHARA) Array, focusing on the H-band MIRC-X and K-band MYSTIC beam combiners. Using the Jones matrix formalism, we developed a comprehensive model describing diattenuation and retardance across the array. By applying this model to an unpolarized calibrator, we derived the instrumental parameters for both MIRC-X and MYSTIC. Our results show differential diattenuation consistent with ≥97% reflectivity per aluminum-coated surface at 45° incidence. The differential retardance exhibits small wavelength-dependent variations, in some cases larger than we expected. Notably, telescope W2 exhibits a significantly larger phase shift in the Coudé path, attributable to a fixed aluminum mirror (M4) used in place of deformable mirrors present on the other telescopes during the observing run. We also identify misalignments in the LiNbO3 birefringent compensator plates on S1 (MIRC-X) and W2 (MYSTIC). After correcting for night-to-night offsets, we achieve calibration accuracies of ±3.4% in visibility ratio and  ±1.°4  in differential phase for MIRC-X, and ±5.9% and  ±2.°4 , respectively, for MYSTIC. Given that the differential intrinsic polarization of spatially resolved sources, such as AGB stars and YSOs, typically greater than these instrumental uncertainties, our results demonstrate that CHARA is now capable of achieving high-accuracy measurements of intrinsic polarization in astrophysical targets.

Keywords: Optical interferometry, Circumstellar dust, Spectropolarimetry
A Systematic Search for Gaseous Debris Disks in DESI Early Data Release White Dwarfs. Detecting gaseous debris disks around white dwarfs offers a unique window into the ultimate fate of planetary systems and the composition of accreted planetary material. Here we present a systematic search for such disks through the Ca II infrared triplet using the Dark Energy Spectroscopic Instrument (DESI) Early Data Release. From a parent sample of 2706 spectroscopically confirmed white dwarfs, we identify 22 candidate systems showing tentative emission-line features, which corresponds to a raw occurrence rate of 0.81%, more than 10 times higher than previous estimates. The detected emission lines are predominantly weak and require confirmation by follow-up observations. Three of these candidates also exhibit infrared excess in Wide-field Infrared Survey Explorer photometry, suggesting a possible coexistence of gas and dust. However, the high candidate rate indicates that most are likely false positives due to telluric residuals or unresolved binaries. This work demonstrates the potential of DESI spectra for blind searches of rare circumstellar phenomena. The recently released DESI DR1, with its substantially larger spectroscopic sample, will enable searches for more gaseous disks and provide better insights into their occurrence and nature.

Keywords: White dwarf stars, Planetary system formation, Infrared excess, Circumstellar disks, Debris disks
An Hα Transit of HD 189733b to Assess Stellar Activity Across the Transit Chord Close to JWST Observations. Transmission spectroscopy allows us to detect molecules in planetary atmospheres, but is subject to contamination from inhomogeneities on the stellar surface. Quantifying the extent of this contamination is essential for accurate measurements of atmospheric composition, as stellar activity can manifest as false atmospheric signals in planetary transmission spectra. We present a study of hot Jupiter HD 189733b, which has over 50 hr of JWST observations scheduled or taken, to measure the activity level of the host star at the current epoch. We utilize high-resolution spectra of the Hα line from the MEGARA spectrograph on the 10 m GTC to examine the activity level of HD 189733 during a transit. We measure Hα becoming shallower midtransit by an Hα index of δ = 0.00156 ± 0.00026, which suggests that HD 189733b crosses an active region as it transits. We posit this deviation is likely caused by a spot along the transit chord with an approximate radius of Rspot = 3.47 ± 0.30R⊕ becoming occulted during transit. Including an approximation for unocculted spots, we estimate that this spot could result in transit depth variations of ∼17 ppm at the 4.3 μm CO2 feature. Since this is comparable to JWST NIRCam Grism mode's noise floor of ∼20 ppm, it could bias atmospheric studies by altering the inferred depths of the planet's features. Thus, we suggest ground-based high-resolution monitoring of activity indicator species concurrently taken with JWST data when feasible to disentangle stellar activity signals from planetary atmospheric signals during transit.

Keywords: High resolution spectroscopy, Hot Jupiters, Exoplanets, Transmission spectroscopy, Stellar activity
Influence of Planetary Flyby Events on Binary Asteroid's Impact Risk. Binary asteroids (BAs) may collide, stay in orbit, or dissociate after a close planetary flyby. The outcome is uncertain due to uncertainties in both the BA's heliocentric orbit and mutual orbit. In the case of dissociation, the two asteroids enter distinct heliocentric orbits. For a slow flyby with a well-determined preflyby heliocentric orbit, the separation between the two asteroids' new heliocentric orbits is found to be comparable to or exceed the uncertainty of the original heliocentric orbit. Consequently, postflyby impact risk assessment based on the original heliocentric orbit is invalid. Furthermore, during a slow flyby, the two asteroids' shapes and rotations, when coupled with the Earth's strong external torque at the perigee, are found to be able to influence the flyby outcome. A critical flyby distance, which varies with the BA's orbit size, is introduced. BAs entering within this critical flyby distance have a high probability to dissociate, necessitating the determination of new heliocentric orbits for the components. For currently known near-Earth BAs, we compute this critical flyby distance and the probability for them to enter within this distance using the well-established line of variation method. Ours analysis indicates that all these BAs are currently moving on safe orbits that do not cross the critical flyby distance in the next 100 yr.

Keywords: Asteroid satellites
Ever Elusive Exospheres: One Probable Detection and Two Nondetections of Hα Transits in Young Systems. Gaps in the exoplanet population, such as the Neptunian Desert, point to the importance of mass loss in sculpting the radii of close-in exoplanets. Young planets (&lt;500 Myr) offer the opportunity to detect such mass loss while it is still strong, and to test models of the underlying physical processes. We search for evidence of an Hα transit in high-resolution spectra of three young planets, HD 63433 b (400 Myr), DS Tuc A b (45 Myr), and HIP 67522 b (17 Myr) using HARPS-N, Magellan-PFS, and CHIRON, respectively. We validate our method by testing it on several photospheric lines less impacted by stellar variability. We find no evidence of a transit signal for HD 63433 b and DS Tuc A b (3σ limits of 0.9% and 0.3%, respectively). For HIP 67522 b, we detect significant excess absorption (3.44% ± 0.28%) aligned with the transit time, narrow compared to the stellar line, and blueshifted from the stellar rest frame. In combination, these suggest the signal is from the planet. However, stellar variation in the Hα line over the course of the observations is comparable in size to the transit signature and the duration is shorter than the photometric transit, so this detection requires confirmation. Our findings, and other recent results in the literature, suggest that planets younger than 50 Myr are more favorable for the detection of atmospheric escape with Hα observations, though older populations might still show escape in other diagnostics.

Keywords: Exoplanets, Exosphere, Hot Neptunes, Transmission spectroscopy, Exoplanet atmospheric evolution
Optical Design of a Near-infrared Spectrograph Prototype for LAMOST. The Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST) has demonstrated exceptional capability in optical spectroscopic surveys. To overcome its inherent limitations in observing late-type stars and regions of high extinction, we present the optical design of a near-infrared (NIR) spectrograph prototype. This instrument is designed to expand LAMOST's spectral coverage into the J band, specifically targeting 900─1400 nm. Driven by key science goals—precise parameter determination for late-type stars and chemical abundance analysis of red supergiants—the design specifications require a spectral resolution R ≥ 1500, a throughput exceeding 35%, and a multiplexing capability of 100 fibers. Confronted with constraints on large-format NIR detector availability, the design employs a 2 × 2 mosaic detector configuration. This necessitates three complementary observing modes, achieved through synchronized rotations of a volume phase holographic grating and the entire NIR optomechanical module, to seamlessly cover the required wavelength range. A critical innovation is the adoption of a fast (F/1.3), fully refractive camera, which avoids the central obscuration of a Schmidt design, thereby enhancing throughput. Optical performance analysis demonstrates that the design meets all requirements: it accommodates 106 fibers, achieves a resolution of 1400─2300 (with a two-thirds slit width), and provides a theoretical peak throughput of 65%. This spectrograph prototype will effectively extend LAMOST's discovery potential into the NIR, enabling groundbreaking studies of Galactic structure and the chemical evolution of nearby galaxies.

Keywords: Mass spectrometers, Astronomical instrumentation
The LMT 2 Millimeter Receiver System (B4R). I. Overview and Results of Science Demonstration. We report on the results of the on-sky test and science demonstration conducted with the 2 mm receiver system, B4R, on the 50 m Large Millimeter Telescope (LMT), located at an altitude of 4600 m in Mexico. The B4R receiver was developed based on the dual-polarization sideband-separating mixer technology of the Atacama Large Millimeter/submillimeter Array and is equipped with a fast Fourier transform digital spectrometer, XFFTS. The primary science objective is the spectroscopic redshift identification of high-redshift dusty star-forming galaxies, complementing the existing 3 mm Redshift Search Receiver by enabling the detection of multiple carbon monoxide lines. Additionally, the B4R receiver broadens the range of science cases possible with the LMT, including astrochemistry, as the 2 mm band encompasses unique molecular lines such as deuterated molecules and shock tracers. During on-site commissioning in 2018 and 2019, we successfully demonstrated on-the-fly mapping and position-switching observations toward the Orion Molecular Cloud 1 and bright high-redshift dusty star-forming galaxies, respectively. We confirmed that the installed B4R system largely met its basic performance specifications. Furthermore, we measured the LMT's aperture efficiencies across the entire B4R frequency range (130─160 GHz), finding them to be roughly consistent with expectations based on a surface accuracy of 100 μm and the receiver optics design. These results with the B4R will enable the most sensitive single-dish spectroscopic observations at 2 mm using the LMT.

Keywords: Millimeter astronomy, Heterodyne receivers, Astrochemistry, Spectroscopy, High-redshift galaxies
SQuIGG<inline-formula> <mml:math><mml:mover><mml:mrow><mml:mi>L</mml:mi></mml:mrow><mml:mrow><mml:mo>→</mml:mo></mml:mrow></mml:mover></mml:math> </inline-formula>E: Buried Star Formation Cannot Explain the Rapidly Fading CO(2─1) Luminosity in Massive, z ∼ 0.7 Post-starburst Galaxies. Observational and theoretical studies have long held that rapid gas consumption in starbursts is responsible for the formation of the most massive quiescent galaxies at high redshift. However, studies of recently quenched "post-starburst" galaxies have discovered that a number of them are surprisingly luminous in CO, challenging this assumption. We present deep Atacama Large Millimeter/submillimeter Array CO(2─1) observations of 50 massive ( log(M⋆/M⊙)∼11.2 ) post-starburst galaxies from the SQuIGG L→ E sample at z ∼ 0.7. We detect a large fraction (27/50) of the galaxies in CO(2─1). We perform new spectral energy distribution (SED) fits incorporating mid- and far-IR photometry to measure the star formation rates (SFRs) and histories that can reproduce both the rest-optical and dust properties of these galaxies. We find that the CO luminosity correlates with the age of the recent starburst, suggesting a gas-removal timescale of ≲150 Myr, an order of magnitude shorter than is implied by their SFRs under standard birth cloud dust assumptions. We find that while allowing for significantly more attenuation in birth clouds can raise SFRs by ∼0.5 dex, for almost all galaxies, it is neither required to fit the observed IR SED, nor is it sufficient to explain the observed depletion trend. Even the combination of significant buried star formation and ULIRG-like αCO is not enough to explain this decay in CO luminosity. Furthermore, there is no strong evidence to support either of those modifications to the depletion time. Therefore, it remains a distinct possibility that the age─CO luminosity trend should not be interpreted as an evolutionary sequence, and that gas-rich SQuIGG L→ E galaxies will soon rejuvenate.

Keywords: Quenched galaxies, Galaxy evolution, Galaxy quenching, High-redshift galaxies, Post-starburst galaxies
An Efficient Shift-and-stack Algorithm Applied to Detection Catalogs. The boundary of solar system object discovery lies in detecting its faintest members. However, their discovery in detection catalogs from imaging surveys is fundamentally limited by the practice of thresholding detections at signal-to-noise (SNR) ≥ 5 to maintain catalog purity. Faint moving objects can be recovered from survey images using the shift-and-stack algorithm, which coadds pixels from multi-epoch images along a candidate trajectory. Trajectories matching real objects accumulate signal coherently, enabling high-confidence detections of very faint moving objects. Applying shift-and-stack comes with high computational cost, which scales with target object velocity, typically limiting its use to searches for slow-moving objects in the outer solar system. This work introduces a modified shift-and-stack algorithm that trades sensitivity for speedup. Our algorithm stacks low-SNR detection catalogs instead of pixels, the sparsity of which enables approximations that reduce the number of stacks required. Our algorithm achieves real-world speedups of 10─103× over image-based shift-and-stack while retaining the ability to find faint objects. We validate its performance by recovering synthetic inner and outer solar system objects injected into images from the DECam Ecliptic Exploration Project. Exploring the sensitivity─compute time trade-off of this algorithm, we find that our method achieves a speedup of ∼30× with 88% of the memory usage while sacrificing 0.25 mag in depth compared to image-based shift-and-stack. These speedups enable the broad application of shift-and-stack to large-scale imaging surveys and searches for faint inner solar system objects. We provide a reference implementation via the find-asteroids Python package and this URL: https://github.com/stevenstetzler/find-asteroids.

Keywords: Surveys, Algorithms, Asteroids, Catalogs