Long-Term Changes of the Supergiant in the X-Ray Binary CYG X-1

Details Long-Term Changes of the Supergiant in the X-Ray Binary CYG X-1 Long-Term Changes of the Supergiant in the X-Ray Binary CYG X-1

Aug 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007iaus..240..122k&link_type=abstract

Binary Stars as Critical Tools and Tests in Contemporary Astrophysics, International Astronomical Union. Symposium no. 240, he

Astronomy and Astrophysics

Astrophysics

Scientific paper

The photometrical and spectral variations point to the supergiant parameter changes on the time scale of tens of years. 35-year long homogeneous photometric series of UBV observations acquired at SAI Crimean Laboratory was used. The object brightness was slowly increasing from 1985 to 1995, and then decreasing to a minimum reached in 2003. The brightness minima were observed in 1971 and in 2003--2005. The largest amplitude was in U band (ΔU=0.1). During the transition from the maximal (1995--1999) to the minimal (2003--2005) brightness, the X-ray activity increased. High-resolution spectra were obtained in 1997 at the Crimean Astrophysical Observatory (the 2.6-m telescope, resolution R=35000) and in 2003-2004 at the Peak Terskol Observatory (the 2-m telescope, R=13000) and BOAO (the 1.8-m telescope, R=30000). Comparison of non-LTE simulations of photometrical variations and HeIλ4713Å line profiles with the observed ones leads to the conclusion that the star radius has increased by about 1-4% from 1997 to 2003-2004 and the supergiant effective temperature decreased by 1300-2400K.

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