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A Partial Near-infrared Guide Star Catalog for Thirty Meter Telescope Operations
Subramaniam, Annapurni; Subramanian, Smitha; Anupama, G. C. +10 more
At first light, the Thirty Meter Telescope (TMT) near-infrared (NIR) instruments will be fed by a multiconjugate adaptive optics instrument known as the Narrow Field Infrared Adaptive Optics System (NFIRAOS). NFIRAOS will use six laser guide stars to sense atmospheric turbulence in a volume corresponding to a field of view of 2', but natural guide…
SDSS J102915.14+172927.9: Revisiting the chemical pattern
Steffen, M.; Ludwig, H. -G.; Bonifacio, P. +7 more
Context. The small- to intermediate-mass (M < 0.8 M⊙), most metal-poor stars that formed in the infancy of the Universe are still shining today in the sky. They are very rare, but their discovery and investigation brings new knowledge on the formation of the first stellar generations. Aims. SDSS J102915.14+172927.9 is one of the most…
The observational evidence that all microflares that accelerate electrons to high energies are rooted in sunspots
Krucker, Säm; Veronig, Astrid M.; Ryan, Daniel F. +6 more
Context. In general, large solar flares are more efficient at accelerating high-energy electrons than microflares. Nonetheless, sometimes microflares that accelerate electrons to high energies are observed. Their origin is unclear. Aims. We statistically characterized microflares with strikingly hard spectra in the hard X-ray (HXR) range, which me…
UOCS. XIII. Study of the Far-ultraviolet Bright Stars in the Open Cluster NGC 2420 Using AstroSat
Bisht, D.; Rangwal, Geeta; Dattatrey, Arvind K. +3 more
We present the study of four far-ultraviolet (FUV) bright stars in the field of the open cluster NGC 2420 using the Ultra Violet Imaging Telescope mounted on AstroSat. The three stars 525, 527, and 560 are members, while star 646 is a nonmember of the cluster. To characterize and determine the parameters of these stars, multiwavelength spectral en…
Astrometric Binary Classification via Artificial Neural Networks
Smith, Joe
With nearly two billion stars observed and their corresponding astrometric parameters evaluated in the recent Gaia mission, the number of astrometric binary candidates has risen significantly. Due to the surplus of astrometric data, the current computational methods employed to inspect these astrometric binary candidates are both computationally e…
Prolonged and Extremely Non-radial Solar Wind Flows
Fujiki, Ken'ichi; Chakrabarty, Dibyendu; Rout, Diptiranjan +3 more
We present a study of three highly non-radial solar wind events in which the azimuthal solar wind flow angle exceeds 6° for one day or more. None of the events are associated with coronal mass ejections and co-rotating interaction regions observed at 1 AU. For all events, the solar wind outflows at 1 AU exhibit low velocity and density. Based on t…
Mg Exosphere of Mercury Observed by PHEBUS Onboard BepiColombo During Its Second and Third Swing-Bys
Korablev, O.; Chaufray, J. -Y.; Leblanc, F. +6 more
Mercury's exosphere is an important target for understanding the dynamics of coupled systems in space environments, tenuous planetary atmospheres, and planetary surfaces. Magnesium (Mg) is especially crucial for establishing methods for estimating the surface chemical composition distribution through observations of the exosphere because its distr…
A multi-instrument study of UV bursts and associated surges in AR 12957
Solanki, S. K.; Berghmans, D.; Calchetti, D. +6 more
Context. The relationship between UV bursts and solar surges is complex, with these events sometimes being observed together and sometimes being observed independently. Why this sporadic association exists is unknown; however, it likely relates to the physical conditions at the site of the energy release that drives these events. Aims. Here, we ai…
OGLE-GD-CEP-0516: The most metal-poor lithium-rich Galactic Cepheid
Salaris, M.; Ripepi, V.; Catanzaro, G. +1 more
Context. Classical Cepheids (DCEPs) are important astrophysical objects not only as standard candles for the determination of the cosmic distance ladder but also as a test-bed for stellar evolution theory thanks to the connection between their pulsation (periods, amplitudes) and stellar (luminosity, mass, effective temperature, metallicity) parame…
Preparation for CSST: Star-galaxy Classification using a Rotationally Invariant Supervised Machine Learning Method
Fang, Guanwen; Lin, Zesen; Kong, Xu +6 more
Most existing star-galaxy classifiers depend on the reduced information from catalogs, necessitating careful data processing and feature extraction. In this study, we employ a supervised machine learning method (GoogLeNet) to automatically classify stars and galaxies in the COSMOS field. Unlike traditional machine learning methods, we introduce se…