X-ray outburst of 4U 0115+634 and ROTSE Observations of its Optical Counterpart V635 Cas

Abstract

ROTSE IIId (The Robotic Optical Transient Experiment) observations of X-ray binary system 4U 0115+634/V635 Cas obtained during 2004 June and 2005 January make possible, for the first time, to study the correlation between optical and type II X-ray outbursts. The X-ray outburst sharply enhanced after periastron passage where the optical brightness was reduced by 0.3 magnitude for a few days. We interpret the sharp reduction of optical brightness as a sign of mass ejection from the outer parts of the disc of the Be star. After this sharp decrease, the optical brightness healed and reached the pre X-ray outburst level. Afterwards, gradual decrease of the optical brightness followed a minimum then a gradual increase started again. Qualitatively, change of optical lightcurve suggests a precession of the Be star disc around a few hundred days. We also investigate the periodic signatures from the archival RXTE-ASM (Rossi X-ray Timing Explorer - All Sky Monitor) light curve covering a time span of $\sim 9$ years. We find significant orbital modulation in the ASM light curve during the type I X-ray outburst.

arXiv comment5 pages, 3 figures, accepted for publication in Astronomy & Astrophysics

References in corpus (6)

• Observations of Accreting Pulsars
• First Results from the All-Sky Monitor on the Rossi X-ray Timing Explorer
• A natural explanation for periodic X-ray outbursts in Be/X-ray binaries
• The ROTSE-III Robotic Telescope System
• The Be/X-ray transient 4U 0115+63/V635 Cas I. A consistent model
• The Be/X-ray transient 4U 0115+63/V635 Cas: II. Outburst mechanisms

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• Large-Scale Image Processing with the ROTSE Pipeline for Follow-Up of Gravitational Wave Events
• A Pipeline for the ROTSE-IIId Archival Data
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