Be/X-ray binary SXP6.85 undergoes large Type II outburst in the Small Magellanic Cloud

Abstract

The Small Magellanic Cloud (SMC) Be/X-ray binary pulsar SXP6.85 = XTE J0103-728 underwent a large Type II outburst beginning on 2008 August 10. The source was consistently seen for the following 20 weeks (MJD = 54688 - 54830). We present X-ray timing and spectroscopic analysis of the source as part of our ongoing Rossi X-ray Timing Explorer (RXTE) monitoring campaign and INTEGRAL key programme monitoring the SMC and 47 Tuc. A comparison with the Optical Gravitational Lensing Experiment (OGLE) III light curve of the Be counterpart shows the X-ray outbursts from this source coincide with times of optical maximum. We attribute this to the circumstellar disk increasing in size, causing mass accretion onto the neutron star. Ground based IR photometry and H-alpha spectroscopy obtained during the outburst are used as a measure of the size of the circumstellar disk and lend support to this picture. In addition, folded RXTE light curves seem to indicate complex changes in the geometry of the accretion regions on the surface of the neutron star, which may be indicative of an inhomogeneous density distribution in the circumstellar material causing a variable accretion rate onto the neutron star. Finally, the assumed inclination of the system and H-alpha equivalent width measurements are used to make a simplistic estimate of the size of the circumstellar disk.

7 pages, 8 figures. This paper has been accepted for publication in MNRAS

References in corpus (6)

• A Long Look at the Be/X-Ray Binaries of the Small Magellanic Cloud
• Spectral distribution of Be/X-ray binaries in the Small Magellanic Cloud
• A 0535+26: Back in business
• Optical and X-ray variability of two Small Magellanic Cloud X-ray binary pulsars - SXP46.6 and SXP6.85
• High mass X-ray binary SXP18.3 undergoes the longest Type II outburst ever seen in the Small Magellanic Cloud
• XMM-Newton observations of the Small Magellanic Cloud: X-ray outburst of the 6.85 s pulsar XTE J0103-728

Cited by in corpus (5)

• On the orbital parameters of Be/X-ray binaries in the Small Magellanic Cloud
• The XMM-Newton survey of the Small Magellanic Cloud: Discovery of the 11.866 s Be/X-ray binary pulsar XMMUJ004814.0-732204 (SXP11.87)
• INTEGRAL deep observations of the Small Magellanic Cloud
• Discovery of the neutron star spin and a possible orbital period from the Be/X-ray binary IGR J05414-6858 in the LMC
• The Orbital Solution and Spectral Classification of the High-Mass X-Ray Binary IGR J01054-7253 in the Small Magellanic Cloud