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10 results on '"Sytov, Alexey"'

1. Verification of Photometric Parallaxes with Gaia DR2 Data

Author

Malkov, Oleg, Karpov, Sergey, Kovaleva, Dana, Sichevsky, Sergey, Chulkov, Dmitry, Dluzhnevskaya, Olga, Kniazev, Alexey, Mickaelian, Areg, Mironov, Alexey, Murthy, Jayant, Sytov, Alexey, Zhao, Gang, and Zhukov, Aleksandr

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract

Results of comparison of Gaia DR2 parallaxes with data derived from a combined analysis of 2MASS (Two Micron All-Sky Survey), SDSS (Sloan Digital Sky Survey), GALEX (Galaxy Evolution Explorer), and UKIDSS (UKIRT Infrared Deep Sky Survey) surveys in four selected high-latitude $|b|>48^{\circ}$ sky areas are presented. It is shown that multicolor photometric data from large modern surveys can be used for parameterization of stars closer than 4400 pc and brighter than $g_{SDSS} = 19.^m6$, including estimation of parallax and interstellar extinction value. However, the stellar luminosity class should be properly determined., Comment: 11 pages, 5 figures

Published
2018

2. Protoplanetary disk shadowing by gas infalling onto the young star AK Sco

Author

de Castro, Ana I. Gomez, Loyd, Robert O. P., France, Kevin, Sytov, Alexey, and Bisikalo, Dmitry

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Young solar-type stars grow through the accretion of material from the circumstellar disk during pre-main sequence (PMS) evolution. The ultraviolet radiation generated in this process plays a key role in the chemistry and evolution of young planetary disks. In particular, the hydrogen Lyman-alpha line (Lya) etches the disk surface by driving photoevaporative flows that control disk evolution. Using the Hubble Space Telescope, we have monitored the PMS binary star AK Sco during the periastron passage and have detected a drop of the H2 flux by up to 10% lasting 5.9 hours. We show that the decrease of the H2 flux can be produced by the occultation of the stellar Lya photons by a gas stream in free fall from 3 R*. Given the high optical depth of the Lya line, a very low gas column of NH > 5e17 cm-2 suffices to block the Lya radiation without producing noticeable effects in the rest of the stellar spectral tracers., Comment: ApJ Letters, accepted. January 25th, 2016

Published
2016
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3. Evaluation of Binary Star Formation Models Using Well-Observed Visual Binaries

Author

Malkov, Oleg, Chulkov, Dmitry, Gebrehiwot, Yikdem, Kovaleva, Dana, Skvortsov, Nikolay A., Sytov, Alexey, Tessema, Solomon Belay, Tutukov, Alexander, Yungelson, Lev, Barbosa, Simone Diniz Junqueira, Editorial Board Member, Filipe, Joaquim, Editorial Board Member, Ghosh, Ashish, Editorial Board Member, Kotenko, Igor, Editorial Board Member, Yuan, Junsong, Editorial Board Member, Zhou, Lizhu, Editorial Board Member, Manolopoulos, Yannis, editor, and Stupnikov, Sergey, editor

Published
2019
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4. Interstellar extinction from photometric surveys: application to four high-latitude areas

Author

Malkov Oleg, Karpov Sergey, Kilpio Elena, Sichevsky Sergey, Chulkov Dmitry, Dluzhnevskaya Olga, Kovaleva Dana, Kniazev Alexei, Mickaelian Areg, Mironov Alexey, Murthy Jayant, Sytov Alexey, Zhao Gang, and Zhukov Aleksandr

Subjects
extinction, surveys, photometry, supernovae, Astronomy, QB1-991
Abstract

Information on interstellar extinction and dust properties may be obtained from modern large photometric surveys data. Virtual Observatory facilities allow users to make a fast and correct cross-identification of objects from various surveys. It yields a multicolor photometry data on detected objects and makes it possible to estimate stellar parameters and calculate interstellar extinction. A 3D extinction map then can be constructed. The method was applied to 2MASS, SDSS, GALEX and UKIDSS surveys. Results for several high-latitude areas are obtained, compared with independent sources and discussed here.

Published
2018
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5. Protoplanetary disk shadowing by gas infalling onto the young star AK Sco.

Author

Gómez de Castro, Ana Inés, Loyd, Robert O. P., France, Kevin, Sytov, Alexey, Bisikalo, Dmitry, Gómez de Castro, Ana Inés, Loyd, Robert O. P., France, Kevin, Sytov, Alexey, and Bisikalo, Dmitry

Abstract

Young solar-type stars grow through the accretion of material from the circumstellar disk during pre-main-sequence (PMS) evolution. The ultraviolet radiation generated in this process plays a key role in the chemistry and evolution of young planetary disks. In particular, the hydrogen Ly alpha line (Ly alpha) etches the disk surface by driving photoevaporative flows that control disk evolution. Using the Hubble Space Telescope, we have monitored the PMS binary star AK. Sco during the periastron passage and have detected a drop of the H-2 flux by up to 10% lasting 5.9 hr. We show that the decrease of the H-2 flux can be produced by the occultation of the stellar Ly alpha photons by a gas stream in free fall from 3. R*. Given the high optical depth of the Ly alpha line, a very low gas column of N-H 5 10 > 10(17) cm(-2) suffices to block the Ly alpha radiation without producing noticeable effects in the rest of the stellar spectral tracers., Ministerio de Economía y Competitividad (MINECO), HST Guest Observer program, Russian Science Foundation, Unidad Deptal. de Astronomía y Geodesia, Fac. de Ciencias Matemáticas, TRUE, pub

Published
2023

6. Verification of Photometric Parallaxes with Gaia DR2 Data

Author

Malkov, Oleg, primary, Karpov, Sergey, additional, Kovaleva, Dana, additional, Sichevsky, Sergey, additional, Chulkov, Dmitry, additional, Dluzhnevskaya, Olga, additional, Kniazev, Alexey, additional, Mickaelian, Areg, additional, Mironov, Alexey, additional, Murthy, Jayant, additional, Sytov, Alexey, additional, Zhao, Gang, additional, and Zhukov, Aleksandr, additional

Published
2018
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9. Interstellar extinction from photometric surveys: application to four high-latitude areas.

Author

Malkov, Oleg, Karpov, Sergey, Kilpio, Elena, Sichevsky, Sergey, Chulkov, Dmitry, Dluzhnevskaya, Olga, Kovaleva, Dana, Kniazev, Alexei, Mickaelian, Areg, Mironov, Alexey, Murthy, Jayant, Sytov, Alexey, Zhao, Gang, and Zhukov, Aleksandr

Subjects
INTERSTELLAR reddening, ASTRONOMICAL photometry, ASTRONOMICAL observatories, SUPERNOVAE, LIGHT absorption
Abstract

Information on interstellar extinction and dust properties may be obtained from modern large photometric surveys data. Virtual Observatory facilities allow users to make a fast and correct cross-identification of objects from various surveys. It yields a multicolor photometry data on detected objects and makes it possible to estimate stellar parameters and calculate interstellar extinction. A 3D extinction map then can be constructed. The method was applied to 2MASS, SDSS, GALEX and UKIDSS surveys. Results for several high-latitude areas are obtained, compared with independent sources and discussed here. [ABSTRACT FROM AUTHOR]

Published
2018
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10. Verification of Photometric Parallaxes with Gaia DR2 Data.

Author

Malkov, Oleg, Karpov, Sergey, Kovaleva, Dana, Sichevsky, Sergey, Chulkov, Dmitry, Dluzhnevskaya, Olga, Kniazev, Alexey, Mickaelian, Areg, Mironov, Alexey, Murthy, Jayant, Sytov, Alexey, Zhao, Gang, and Zhukov, Aleksandr

Subjects
ASTROMETRY, INTERSTELLAR reddening, ASTRONOMICAL surveys, GALACTIC evolution, PARALLAX, LUMINOSITY
Abstract

Results of comparison of Gaia DR2 parallaxes with data derived from a combined analysis of 2MASS (Two Micron All-Sky Survey), SDSS (Sloan Digital Sky Survey), GALEX (Galaxy Evolution Explorer), and UKIDSS (UKIRT Infrared Deep Sky Survey) surveys in four selected high-latitude | b | > 48° sky areas are presented. It is shown that multicolor photometric data from large modern surveys can be used for parameterization of stars closer than 4400 pc and brighter than g S D S S = 19. m 6 , including estimation of parallax and interstellar extinction value. However, the stellar luminosity class should be properly determined. [ABSTRACT FROM AUTHOR]

Published
2019
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