Volume 378, Number 3, November II 2001
|Page(s)||837 - 842|
|Section||Interstellar and circumstellar matter|
|Published online||15 November 2001|
X-ray and optical periodicities in X-ray binaries I. A0535+26
Astronomical Institute of St. Petersburg University, Petrodvorets, Bibliotechnaya Pl. 2, 198504, Russia
2 Isaac Newton Institute of St. Petersburg, Chile, St. Petersburg Branch, Russia
3 P. K. Shternberg Astronomical Institute, Moscow, Russia
Corresponding author: V. Larionov, VML@VL1104.spb.edu
Accepted: 26 July 2001
A homogeneous set of UBV photometry (354 data points obtained between 1983 and 1998) for the Be/X-ray binary A0535+26 = V725 Tau is analysed, aiming to look for possible periodic component(s). After subtraction of the long-term variation it was found that only a 103d periodic component remains in the power spectra in both the V and B colour bands. The probability of chance occurrence of such a peak is less than 0.1% . There are no signs of optical variability at the X-ray period (111d). We discuss possible reasons for a 103-day modulation and suggest that it corresponds to a beat frequency of the orbital period of the neutron star and the precession period (1400d) either of an accretion disc around the neutron star or a warped decretion disc around the Be star.
Key words: stars: binaries: general / stars: circumstellar matter / stars: individual: V725 Tau / stars: pulsars: individual: A0535+26 / stars: variables: general / accretion, accretion discs
© ESO, 2001
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