Optical Follow-up of New SMC Wing Be/X-ray Binaries

Abstract

We investigate the optical counterparts of recently discovered Be/X-ray binaries in the Small Magellanic Cloud. In total four sources, SXP101, SXP700, SXP348 and SXP65.8 were detected during the Chandra Survey of the Wing of the SMC. SXP700 and SXP65.8 were previously unknown. Many optical ground based telescopes have been utilised in the optical follow-up, providing coverage in both the red and blue bands. This has led to the classification of all of the counterparts as Be stars and confirms that three lie within the Galactic spectral distribution of known Be/X-ray binaries. SXP101 lies outside this distribution becoming the latest spectral type known. Monitoring of the Halpha emission line suggests that all the sources bar SXP700 have highly variable circumstellar disks, possibly a result of their comparatively short orbital periods. Phase resolved X-ray spectroscopy has also been performed on SXP65.8, revealing that the emission is indeed harder during the passage of the X-ray beam through the line of sight.

arXiv comment9 pages, 9 figures, 2 tables, accepted for publication in MNRAS

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Cited by in corpus (8)

• Be/X-ray binaries
• High-Mass X-ray binaries in the Small Magellanic Cloud
• Star formation history and X-ray binary populations: the case of the Small Magellanic Cloud
• Spectral distribution of Be/X-ray binaries in the Small Magellanic Cloud
• The Runaways and Isolated O-Type Star Spectroscopic Survey of the SMC (RIOTS4)
• The First Year of S-CUBED: The Swift Small Magellanic Cloud Survey
• The Chandra Small Magellanic Cloud Wing Survey - the search for X-ray Binaries
• High mass X-ray binary SXP18.3 undergoes the longest Type II outburst ever seen in the Small Magellanic Cloud