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On the long-term variability of high massive X-ray binary Cyg X-1

Published online by Cambridge University Press:  30 December 2019

Eugenia Karitskaya Open the ORCID record for Eugenia Karitskaya [Opens in a new window] ,
Nikolai Bochkarev ,
Vitalij Goranskij  and
Natalia Metlova
Eugenia Karitskaya
Affiliation:
Institute of Astronomy RAS, 48 Pyatnitskaya Str., Moscow, Russia. email: karitsk@yandex.ru
Nikolai Bochkarev
Affiliation:
Sternberg Astronomical Institute Lomonosov Moscow State University, Moscow, Russia
Vitalij Goranskij
Affiliation:
Sternberg Astronomical Institute Lomonosov Moscow State University, Moscow, Russia
Natalia Metlova
Affiliation:
Sternberg Astronomical Institute Lomonosov Moscow State University, Moscow, Russia
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Abstract

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. We continue our study of spectral and photometric variability of Cyg X-1 on the basis of the 45-year long series of multicolor photometric observations and many-year-long series of spectral observations we have accumulated up to now. The mean level of star brightness continues to decrease since 1999 with the variations on smaller time scales superimposed. There is a connection between X-ray and optical changes. The chaotic variations of X-ray flux sometimes reaching to “hard” - “soft” state irregular changes switch on when U brightness decrease and He I λ 4713 Å absorption line depth increase. And inversely - they switch off during U brightness increasing and He I λ 4713 Å absorption line depth decreasing. This may be connected with star size variations, causing outflow gas instability. It is concluded that the fundamental parameters of the supergiant in the system of Cyg X-1 continue to vary on the time scales of years - decades.

Keywords

stars: individual (HD 226868 V1357 Cyg Cyg X-1)stars: variables: Cyg X-1stars: fundamental parametersstars: O-supergiantstars: spectral variationsstars: photometrical variations
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 14 , Symposium S346: High-mass X-ray Binaries: Illuminating the Passage from Massive Binaries to Merging Compact Objects , August 2018 , pp. 206 - 211
Copyright
© International Astronomical Union 2019 

References

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