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The Pleiades apex and its kinematical structure
Yadav, R. K. S.; Vereshchagin, S. V.; Chupina, N. V. +4 more
A study of cluster characteristics and internal kinematical structure of the middle-aged Pleiades open star cluster is presented. The individual star apexes and various cluster kinematical parameters including the velocity ellipsoid parameters are determined using both Hipparcos and Gaia data. Modern astrometric parameters were taken from the Gaia…
A simultaneous spectroscopic and photometric study of two eclipsing binaries: V566 Oph and V972 Her
Yılmaz, M.; Selam, S. O.; Esmer, E. M. +4 more
In this study, we have performed simultaneous solutions of light and radial velocity curves of two eclipsing binary systems, V566 Oph and V972 Her. We observed both systems spectroscopically with a very recently installed spectrograph on the 40 cm telescope, T40, located in Ankara University Kreiken Observatory (AUKR), for the first time. We made …
A study of pulsation & rotation in a sample of A-K type stars in the Kepler field
Paul, K. T.; Engelbrecht, Chris A.; Joshi, Santosh +3 more
We present the results of time-series photometric analysis of 15106 A-K type stars observed by the Kepler space mission. We identified 513 new rotational variables and measured their starspot rotation periods as a function of spectral type and discuss the distribution of their amplitudes. We examined the well-established period-color relationship …
Memberships, distance and proper-motion of the open cluster NGC 188 based on a machine learning method
Gao, Xin-Hua
In this paper, we present an investigation of the memberships, distance and proper motion for the old open cluster NGC 188 using a machine-learning-based method. This method combines two widely used algorithms: spectral clustering (SC) and random forest (RF). The former one is used to construct a reliable training set, the membership probabilities…
Protostellar classification using supervised machine learning algorithms
Miettinen, O.
Classification of young stellar objects (YSOs) into different evolutionary stages helps us to understand the formation process of new stars and planetary systems. Such classification has traditionally been based on spectral energy distribution (SED) analysis. An alternative approach is provided by supervised machine learning algorithms, which can …
The global modulation of Galactic and Jovian electrons in the heliosphere
Potgieter, Marius S.; Nndanganeni, Rendani R.
A full three-dimensional, numerical model is used to study the modulation of Jovian and Galactic electrons from 1 MeV to 50 GeV, and from the Earth into the heliosheath. For this purpose the very local interstellar spectrum and the Jovian electron source spectrum are revisited. It is possible to compute the former with confidence at kinetic energi…
Pulse phase-resolved analysis of SMC X-3 during its 2016–2017 super-Eddington outburst
Weng, Shan-Shan; Ge, Ming-Yu; Zhao, Hai-Hui +2 more
The Be X-ray pulsar SMC X-3 underwent an extra long and ultraluminous giant outburst from 2016 August to 2017 March. The peak X-ray luminosity is up to
The broad-band spectrum of the narrow-line Seyfert 1 NGC 4748: from UV to hard X-ray
Vasylenko, A. A.
We report the results obtained by a broad-band (0.5–500 keV) data analysis of narrow-line Seyfert 1 galaxy NGC 4748 observed with an XMM-Newton/PN, INTEGRAL/ISGRI and SWIFT/BAT telescopes. This galaxy has a soft X-ray excess that is typical for the class of narrow-line Seyfert 1. The question of the origin of soft excess in such objects is still u…
Using GALEX-SDSS-PanSTARRS-HST-Gaia to understand post-AGB evolution
Bianchi, Luciana; Casewell, Sarah; Bohlin, Ralph +2 more
Hot WDs in binary systems with a less evolved star are particularly invaluable astrophysical probes, the unevolved companion enabling better derivation of distance and age than is usually possible for post-AGB objects, and therefore also of their radius and luminosity. But hot white dwarfs (WD) are elusive at all wavelengths except the UV (Bianchi…
UV astronomy throughout the ages: a historical perspective
Linsky, Jeffrey L.
Astronomers have long recognized the critical need for ultraviolet imaging, photometry and spectroscopy of stars, planets, and galaxies, but this need could not be satisfied without access to space and the development of efficient instrumentation. When UV measurements became feasible, first with rockets and then with satellites, major discoveries …