Sazuna/UAT_keywords huggingface dataset:
Tracing the Galactic Origins of Selected Four G-type Stars in the Solar Neighborhood. We present a multimethod investigation of four metal-poor G-type main-sequence stars to resolve their Galactic origins. By combining high-resolution spectroscopy from PolarBase, photometric/astrometric data from Gaia DR3, and spectral energy distribution modeling, we derive precise stellar parameters, chemical abundances, kinematics, and Galactic orbital parameters. The stars HD 22879, HD 144579, HD 188510, and HD 201891 show effective temperatures of 5855 ± 110, 5300 ± 160, 5370 ± 60, and 5880 ± 90 K; surface gravities of 4.40 ± 0.18, 4.52 ± 0.37, 4.57 ± 0.13, and 4.48 ± 0.18 cgs; and metallicities of ‑0.86 ± 0.08, ‑0.55 ± 0.12, ‑1.60 ± 0.07, and ‑1.15 ± 0.07 dex, respectively. Kinematic analysis suggests that HD 22879, HD 144579, and HD 201891 are potential bulge-origin escapees, possibly ejected by the Galactic bar or spiral arm perturbations. HD 188510, however, shows halo-like dynamics, including a retrograde orbit. Chemical abundance trends ([α/Fe] versus [Fe/H]) reveal mixed origins, challenging kinematic classifications. This discrepancy highlights the importance of integrative methodologies in Galactic archaeology. We associate HD 22879, HD 144579, and HD 201891 with the bulge globular cluster NGC 6441, NGC 5927, and NGC 6544, respectively. HD 188510's retrograde motion and low metallicity align with ejection from the halo globular cluster NGC 5139 (ω Cen). These results illustrate the complex interplay of dynamical processes—including bar resonances, spiral arm perturbations, and tidal stripping—in depositing metal-poor stars into the solar neighborhood.

Keywords: Stellar kinematics, Stellar dynamics, Solar neighborhood, Chemical abundances
A Search for Exoplanet Candidates in TESS 2 minute Light Curves Using Joint Bayesian Detection. In this work, we apply an exploratory joint Bayesian transit detector, previously evaluated using Kepler data, to the 2 minutes simple aperture photometry light-curve data in the continuous viewing zone for the Transiting Exoplanet Survey Satellite (TESS) over 3 yr of observation. The detector uses Bayesian priors, adaptively estimated, to model unknown systematic noise and stellar variability incorporated in a Neyman–Pearson likelihood ratio test for a candidate transit signal; a primary goal of the algorithm is to reduce overfitting. The detector was adapted to the TESS data and refined to improve outlier rejection and suppress FA detections in postprocessing. The statistical performance of the detector was evaluated using transit injection tests, where the joint Bayesian detector achieves an 80.0% detection rate and a 19.1% quasi-false-alarm rate at a detection threshold τ = 10; this is a marginal, although not statistically significant, improvement of 0.2% over a reference sequential detrending and detection algorithm. In addition, a full search of the input TESS data was performed to evaluate the recovery rate of known TESS Objects of Interest (TOIs) and to perform an independent search for new exoplanet candidates. The joint detector has a 73% recall rate and a 63% detection rate for known TOIs; the former considers a match against all detection statistics above threshold, while the latter considers only the maximum detection statistic.

Keywords: Bayesian statistics, Likelihood ratio test, Transit instruments, Exoplanets, Light curves, Astronomy data analysis, Astrostatistics, Computational methods, Photometry, Transit photometry
Measuring Long Stellar Rotation Periods (&gt;10 days) from TESS FFI Light Curves is Possible: An Investigation Using TESS and ZTF. The rotation period of a star is an important quantity that provides insight into its structure and state. For stars with surface features like starspots, their periods can be inferred from brightness variations as these features move across the stellar surface. TESS, with its all-sky coverage, is providing the largest sample of stars for obtaining rotation periods. However, most of the periods have been limited to shorter than the 13.7 days TESS orbital period due to strong background signals (e.g., scattered light) on those timescales. In this study, we investigated the viability of measuring longer periods (&gt;10 days) from TESS light curves for stars in the Northern Continuous Viewing Zone (NCVZ). We first created a reference set of 272 period measurements longer than 10 days for K and M dwarfs in the NCVZ using data from the Zwicky Transient Facility (ZTF) that we consider as the "ground truth" given ZTF's long temporal baseline of 6+ years. We then used the unpopular pipeline to detrend TESS light curves and implemented a modified Lomb–Scargle (LS) periodogram that accounts for flux offsets between observing sectors. For 179 out of the 272 sources (66%), the TESS-derived periods match the ZTF-derived periods to within 10%. The match rate increases to 81% (137 out of 170) when restricting to sources with a TESS LS power that exceeds a threshold. Our results confirm the capability of measuring periods longer than 10 days from TESS data, highlighting the data set's potential for studying slow rotators.

Keywords: M dwarf stars, Sky surveys, Light curves, Lomb-Scargle periodogram, Astronomy data analysis, Dwarf stars, K dwarf stars, Stellar rotation
DESI Mg II Absorbers: Extinction Characteristics and Quasar Redshift Accuracy. In this paper, we study how absorption-line systems affect the spectra and redshifts of quasi-stellar objects (QSOs), using catalogs of Mg II absorbers from the early data release and first data release of the Dark Energy Spectroscopic Instrument. We determine the reddening effect of an absorption system by fitting an unreddened template spectrum to a sample of 50,674 QSO spectra that contain Mg II absorbers. We find that reddening caused by intervening absorbers (voff &gt; 3500 km s‑1) has an average color excess of  E(B‑V)¯  = 0.04 mag. We find that the E(B ‑ V) tends to be greater for absorbers at low redshifts, or those having Mg II absorption lines with higher equivalent widths, but shows no clear trend with voff for intervening systems. However, the  E(B‑V)¯  of associated absorbers, those at voff &lt; 3500 km s‑1, shows a strong trend with voff, increasing rapidly with decreasing voff and peaking (∼0.15 mag) around voff = 0 km s‑1. We demonstrate that Mg II absorbers impact redshift estimation for QSOs by investigating the distributions of voff for associated absorbers. We find that at z &gt; 1.5, these distributions broaden and bifurcate in a nonphysical manner. In an effort to mitigate this effect, we mask pixels associated with the Mg II absorption lines and recalculate the QSO redshifts. We find that we can recover voff populations in better agreement with those for z &lt; 1.5 absorbers and in doing so typically shift background QSO redshifts by Δz ≈ ± 0.005.

Keywords: Quasar absorption line spectroscopy, Large-scale structure of the universe, Quasars, Observational cosmology, Intergalactic gas, Extragalactic astronomy
Was there a (Super)nova in 1408?. The 1408 CE "guest star" recorded in Chinese historical texts presents a compelling case for identifying a historical stellar transient. While previous studies debated its nature as a meteor, comet, or nova, we reevaluate the event using original Ming Dynasty records, including a newly found memorial from the imperial court. The object, described as stationary for over 10 days, yellow, and luminous (resembling a "Zhou Bo virtue star"), is inconsistent with cometary behavior. Positional analysis locates it near the Niandao asterism (modern Cygnus–Vulpecula region) within the Milky Way, with a derived brightness of ‑4 to 0 mag. Lightcurve stability over 10 days and color descriptions align with a slow nova or a supernova. We cross-correlated the historical coordinates with modern catalogs and found a few possible counterparts. Among them, CK Vul—a luminous red nova remnant from 1670 to 1672—is the most interesting candidate. Could its progenitor system have experienced a precursor classical nova eruption circa 1408 prior to the merger ∼200 yr later? We also examine cataclysmic variables and planetary nebulae within the 100 square-degree search field, though most lack sufficient brightness or age characteristics. This study emphasizes the value of integrating detailed historical records with contemporary astrophysical data to resolve long-standing controversies over ancient transients. The 1408 event likely represents a rare, well-documented nova, offering insights into premodern stellar phenomena and their modern counterparts.

Keywords: Ultraviolet astronomy, Interdisciplinary astronomy, History of astronomy, Classical novae
Abundance Measurements of the Metal-poor M Subdwarf LHS 174 Using High-resolution Optical Spectroscopy. Metal-poor M subdwarfs are among the oldest stellar populations and carry valuable information about the chemical enrichment history of the Milky Way. The measurements of chemical abundances of these stars therefore provide essential insights into the nucleosynthesis in the early stages of the Galaxy's formation. We present detailed spectroscopic analysis of a nearby metal-poor M subdwarf, LHS 174, from its high-resolution optical spectrum, and apply our previously developed spectral fitting code, AutoSpecFit, to measure the abundances of five elements: [O/H] = ‑0.519±0.081, [Ca/H] = ‑0.753 ± 0.177, [Ti/H] = ‑0.711 ± 0.144, [V/H] = ‑1.026 ± 0.077, and [Fe/H] = ‑1.170 ± 0.135. We compare the abundances of O, Ti, and Fe derived from this work and those from previous studies, and demonstrate the observed data are clearly better matched with the synthetic model generated based on our abundances than those from the other analyses. The accuracy of inferred stellar abundances strongly depends on the accuracy of physical parameters, which motivates us to develop a reliable technique to more accurately determine the parameters of low-mass M dwarfs and infer abundances with smaller uncertainties.

Keywords: M dwarf stars, Stellar abundances, M subdwarf stars
The Initial Mass Function of Stars and Brown Dwarfs in the Upper Sco Association. I present infrared spectroscopy of 37 brown dwarf candidates in the Upper Scorpius (Upper Sco) association, 35 of which are classified as young and cool, making them likely members. This sample includes many of the faintest spectroscopically confirmed members (K = 16─17 mag), which should have masses down to ∼0.007─0.01 M⊙ for the range of ages in Upper Sco (7─14 Myr). Using my updated membership catalog for Upper Sco, I have estimated the initial mass function (IMF) for a field in the center of the association that encompasses ∼80% of the known members. I have derived IMFs in the same manner for previous membership samples in three other star-forming populations, consisting of IC 348, Taurus, and Chameleon I. When using logarithmic mass bins, the substellar IMFs for Upper Sco and the other young regions are roughly flat down to the completeness limits of ∼0.01 M⊙. These IMFs are broadly similar to mass functions recently measured for the solar neighborhood. Finally, I have used W1−W2 colors to search for excess emission from circumstellar disks among the late-type objects in my new census of Upper Sco. I measure an excess fraction of 52/200 for members with spectral types of M6.25─M9.5, which is similar to results from previous membership catalogs. For the L-type members, it is difficult to detect the small W2 excess emission produced by typical disks around brown dwarfs because of the large uncertainties in spectral types, which preclude accurate estimates of the photospheric colors. Thus, W2 photometry provides poor constraints on the presence of disks for the L-type members of Upper Sco. *Based on observations made with the Gaia mission, the Two Micron All Sky Survey, the Wide-field Infrared Survey Explorer, the United Kingdom Infrared Telescope Infrared Deep Sky Survey, the Visible and Infrared Survey Telescope for Astronomy Hemisphere Survey, Pan-STARRS1, the NASA Infrared Telescope Facility, Cerro Tololo Inter-American Observatory, Gemini Observatory, and the European Southern Observatory.

Keywords: Brown dwarfs, Initial mass function, Star forming regions, L dwarfs, Star formation, Circumstellar disks
Reduced Solar Quadrupole Moment Compensates for Lack of Asteroids in Long-term Solar System Integrations. State-of-the-art long-term solar system integrations include several second order effects such as the Sun's quadrupole moment J2 and a contribution from asteroids (plus the Moon and general relativity). We recently showed that including 10 asteroids and a reduced J2 in our astronomical solutions provides the best match with geologic data to ‑58 Myr. However, the rationale for the reduced J2 remained ambiguous and may suggest that parameters for long-term integrations compatible with geologic observations are not fully compatible with our knowledge of the current solar system (specifically J2). Here we show that a reduced J2 compensates for a diminished asteroid population in long-term solar system integrations, which may appear surprising. We present an analysis and offer a mechanism for the long-term compensating effects of J2 and asteroid mass in the solar system (not planetary systems in general). Our analysis suggests that "differential effects" on specific secular frequencies involved in resonant terms (i.e., (g4 ‑ g3) and (s4 ‑ s3)), are critical in the long term, rather than short-term effects on the orbital elements of individual planetary orbits across the board. Also, our results indicate that if long-term integrations including the full asteroid population were computationally feasible, a J2 value (within errors) compatible with our current knowledge of the solar system could be used. Attempts to improve the long-term accuracy of astronomical solutions by, e.g., tinkering with initial conditions using current/future astronomical observations are futile unless asteroid deficiencies in the solar system model are addressed.

Keywords: Orbits, Solar system, N-body simulations, Dynamical evolution
Additive Attention for Vetting Transiting Exoplanet Candidates. In this study we propose a deep learning model architecture using long short-term memory (LSTM) networks and additive attention mechanisms for vetting transiting exoplanet candidates. Our method is applied to two different data sets (Kepler and TESS) comprising light curves, representing periodic fluctuations in star brightness that are potentially indicative of planetary transits. Making use of preprocessed data from the Kepler and TESS missions, we evaluate the effectiveness of LSTM-based approaches in contrast to conventional CNN methods. Through extensive experimentation, we demonstrate the efficacy of our final model, which integrates CNN, LSTM, and additive attention layers, coupled with feed-forward neural networks, achieving competitive performance with limited model complexity. Notably, the incorporation of additive attention enhances prediction accuracy across various model scales without significantly increasing model complexity. Our findings highlight the utility of additive attention in vetting transiting exoplanet candidates, offering understanding of the model decision-making processes. Overall, our proposed architecture presents a general-purpose approach for addressing transit detection challenges across different data sets, contributing to advancements in astronomical data analysis.

Keywords: Neural networks, Convolutional neural networks, Exoplanet astronomy, Exoplanet detection methods, Transit photometry
A Demonstration of Interstellar Navigation Using New Horizons. As NASA's New Horizons spacecraft exits the solar system bound for interstellar space, it has traveled so far that the nearest stars have shifted markedly from their positions seen from Earth. We demonstrated this by imaging the Proxima Centauri and Wolf 359 fields from Earth and New Horizons on 2020 April 23, when the spacecraft was 47.1 au distant. The observed parallaxes for Proxima Centauri and Wolf 359 are  32.″4  and  15.″7 , respectively. These measurements are not of research grade, but directly seeing large stellar parallaxes between two widely separated simultaneous observers is vividly educational. Using the New Horizons positions of the two stars alone, referenced to the three-dimensional model (3D) of the solar neighborhood constructed from Gaia DR3 astrometry, further provides the spacecraft spatial position relative to nearby stars with 0.44 au accuracy. The range to New Horizons from the solar system barycenter is recovered to 0.27 au accuracy, and its angular direction to  0.°4  accuracy, when compared to the precise values from NASA Deep Space Network tracking. This is the first time optical stellar astrometry has been used to determine the 3D location of a spacecraft with respect to nearby stars and the first time any method of interstellar navigation has been demonstrated for a spacecraft on an interstellar trajectory. We conclude that the best astrometric approach to navigating spacecraft on their departures to interstellar space is to use a single pair of the closest stars as references, rather than a large sample of more distant stars.

Keywords: Space probes, Space astrometry
100 Proof: H I Observations of 100 Nearby Dwarf Galaxies with the 100 m Green Bank Telescope. We describe the results of observations with the 100 m Robert C. Byrd Green Bank Telescope in the H I line of 105 nearby dwarf galaxies, 60 of which were discovered recently in the DESI Legacy Imaging Surveys. Of 105 objects observed, we detected 77 galaxies with the following median parameters: an H I flux of 0.69 Jy km s‑1, a heliocentric velocity of 732 km s‑1, and a W50 line width of 32 km s‑1. Seventy are isolated late-type objects and 35 are new probable satellites of nearby spiral galaxies (NGC 628, NGC 2787, NGC 3556, NGC 4490, NGC 4594, and NGC 5055). The detected galaxies are predominantly gas-rich systems with a median gas-to-stellar-mass ratio of 1.87. In general, they follow the classic Tully–Fisher relation obtained for large disk-dominated spiral galaxies if their M21 magnitudes are used instead of B magnitudes.

Keywords: Dwarf irregular galaxies, Irregular galaxies, Dwarf galaxies, Galaxy distances
Multiple Generation Star Formation in Cepheus Flare. We present an analysis of the young stellar moving group ASCC 127 using Gaia DR3 data, significantly expanding its membership to 3971 stars—double the number identified in previous studies. Using kinematic and distance criteria, ASCC 127 is divided into five subgroups (Groups 1‑5) with ages spanning from 15 to 32 Myr. Groups 1‑5 are spatially linked to the Cepheus Flare star-forming region, revealing potential evidence of four sequential star formation episodes at approximately 32 Myr, 20 Myr, 15 Myr, and 7 Myr. Through dust and gas mapping, we identify a spatial cavity extending several tens of parsecs, which may have resulted from feedback processes such as supernovae associated with earlier generations of stars in the region. This structure, along with the larger Loop III feature, indicates that feedback from massive stars likely influenced the interstellar medium (ISM). By integrating young stellar populations with ISM studies, we provide a detailed picture of the feedback-driven star-formation history in the Cepheus Flare region.

Keywords: Moving clusters, Star forming regions
Mars Orientation Parameters Estimation with Simulated Same Beam Interferometry. The accurate determination of Mars orientation parameters (MOP) is essential for investigating the internal structure, seasonal variations of polar dry ice, and dynamic evolution of Mars. Current methods rely on Doppler and range tracking between Earth ground station and Mars lander, which are constrained by ionospheric, tropospheric and other errors. Same-beam interferometry (SBI), employing two Earth ground stations simultaneous to observe two Mars landers, effectively mitigates common-mode errors by leveraging differential phase measurements. We evaluate the accuracy enhancement of SBI in resolving MOP, key findings include: SBI with landers at lower latitudes and larger longitude difference yields higher accuracy; SBI alone is unsuitable for MOP due to its lower sensitivity to parameters compared to two-way Doppler and two-way range most of time; Combining with SBI data, two-way Doppler improves the accuracy of precession rate ( ψ̇0 ), obliquity rate ( İ0 ), and spin rate ( ϕ̇0 ) by up to 43%, and reduced the correlation between some parameters, for certain rigid amplitudes, length-of-day (LOD) variation and polar motion parameters, there are different durations and degrees of accuracy improvement before the 700th mission day. Two-way range integrated with SBI achieves up to 45% precision gain about these three parameters, for certain rigid amplitudes and LOD variation, there are also different durations and degrees of accuracy improvement before the 600th mission day, with no significant improvement in polar motion parameters. SBI has duration selectivity and observation mode dependence for the improvement, and low-noise and low-latitude lander distribution can further extend the accuracy improvement duration.

Keywords: Mars, Landers, Astronomical simulations
Closeby Habitable Exoplanet Survey (CHES). IV. Synergy between Astrometry and Direct Imaging Missions of the Habitable World Observatory for Detecting Earth-like Planets. The detection and characterization of habitable planets around nearby stars persist as some of the foremost objectives in contemporary astrophysics. This work investigates the synergistic integration of astrometric and direct imaging techniques by capitalizing on the complementary capabilities of the Closeby Habitable Exoplanet Survey (CHES) and Habitable Worlds Observatory (HWO). Planetary brightness and position vary over time due to phase effects and orbital architecture, information that can be precisely provided by CHES's astrometric measurements. By combining the precise orbital constraints from CHES with the imaging capabilities of HWO, we evaluate the improvements in detection efficiency, signal-to-noise ratio, and overall planet yield. Completeness is quantified as the fraction of injected planets that are successfully detected, while yields are estimated for various scenarios using terrestrial planet occurrence rates derived from the Kepler data set. Our results indicate that prior astrometric data significantly enhance detection efficiency. Under the adopted detection limit, our analysis indicates that prior CHES observations can increase completeness by approximately 10% and improve detection efficiency by factors ranging from 2 to 30. The findings underscore the importance of interdisciplinary approaches in the search for and characterization of habitable worlds.

Keywords: Exoplanet detection methods, Direct imaging, Astrometric exoplanet detection