Search Publications
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…
Measurement of interstellar extinction for classical T Tauri stars using far-UV H2 line fluxes
France, K.; Eislöffel, J.; Schneider, P. C. +3 more
Understanding the interstellar and potentially circumstellar extinction in the sight lines of classical T Tauri stars is an important ingredient for constructing reliable spectral energy distributions, which catalyze protoplanetary disk chemistry, for example. Therefore, some attempts of measuring AV toward individual stars have been ma…
In pursuit of precise Ca II H&K chromospheric surface fluxes: A gravity and temperature dependence
Schröder, K. -P.; Jack, D.; Rosas-Portilla, F.
The emission lines of the Ca II H&K doublet present one of the most important channels of radiative cooling for the chromospheres of cool stars. Although most other line emissions (Mg II h&k and numerous iron lines) populate the far-UV and require a very competitive space-born observing time, the Ca II H&K lines in the optical UV are easily access…
Verification of Hypervelocity Bulge Red Clump Stars
Poleski, Radosław; Wojtkowska, Gabriela
We verify candidate hypervelocity red clump stars located in the Galactic bulge that were selected based on the VVV and the Gaia DR2 data by Luna et al. To do so, we analyze data from the OGLE-IV survey: difference images and astrometric time series. We have data for 30 stars out of 34 hypervelocity candidates. We confirmed the high proper motion …