Long-term variability of the Be/X-ray binary A 0535+26 – I. Optical and UV spectroscopy |
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| Authors: | Clark Tarasov Steele Coe Roche Shrader Buckley Larionov Larionova Lyuty Zaitseva Grunsfeld Fabregat & Parise |
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| Institution: | Physics Department, University of Southampton, Southampton SO17 1BJ,;Crimean Astrophysical Observatory, Ukraine, 334413, Nauchny, Crimea, Ukraine,;Astrophysics Group, Liverpool John Moores University, Liverpool L3 3AF,;Astronomy Centre, MAPS, University of Sussex, Brighton BN1 9QH,;NASA/Goddard Space Flight Center, MD20771, USA,;South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa,;Astronomical Institute, St Petersburg University, 198904, St Petersburg, Russia,;Departamento de Mathematica Aplicada y Astronomia, Universidad de Valencia, 46100 Burjassot, Valencia, Spain |
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| Abstract: | The results of a 7-yr optical and UV spectroscopic study of the high-mass X-ray binary A 0535+26 are presented. It was found that throughout the period of the observations the line profile of Hα showed considerable variability. A correlation between the equivalent width of Hα and both V -band magnitude and ( B − V ) colour excess was observed, albeit with considerable scatter present in the data set. A giant X-ray flare in early 1994 was accompanied by a fading in optical and infrared photometric bands, and a reduction in the equivalent width of Hα. When the star was observed in 1994 September, it was found to have developed a double-peaked Hα profile, and further observations saw the V/R peak ratio vary cyclically, with a period of ∼1 yr. If this is identified as a global one-armed oscillation, it becomes the shortest period ever observed in a Be star. The accompanying photometric and spectroscopic observations provide a test of any theory seeking to describe the onset and behaviour of such a density wave. |
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| Keywords: | binaries: close stars: emission-line Be pulsars: individual: A 0535+26 X-rays: stars |
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