SXP 7.92: a recently rediscovered Be/X-ray binary in the Small Magellanic Cloud, viewed edge on
Date Issued
2017
Author(s)
Abstract
We present a detailed optical and X-ray study of the 2013 outburst of the Small Magellanic Cloud Be/X-ray binary SXP 7.92, as well as an overview of the last 18 years of observations from OGLE (Optical Gravitational Lensing Experiment), RXTE, Chandra and XMM-Newton. We revise the position of this source to RA(J2000) = 00:57:58.4, Dec(J2000) = -72:22:29.5 with a 1σ uncertainty of 1.5 arcsec, correcting the previously reported position by Coe et al. by more than 20 arcmin. We identify and spectrally classify the correct counterpart as a B1Ve star. The optical spectrum is distinguished by an uncharacteristically deep narrow Balmer series, with the Hα line in particular having a distinctive shell profile, I.e. a deep absorption core embedded in an emission line. We interpret this as evidence that we are viewing the system edge on and are seeing self-obscuration of the circumstellar disc. We derive an optical period for the system of 40.0 ± 0.3 d, which we interpret as the orbital period, and present several mechanisms to describe the X-ray/optical behaviour in the recent outburst, in particular the 'flares'and 'dips' seen in the optical light curve, including a transient accretion disc and an elongated precessing disc.
Volume
466
Issue
4
Start page
4659
Issn Identifier
0035-8711
Ads BibCode
2017MNRAS.466.4659B
Rights
open.access
File(s)![Thumbnail Image]()
Loading...
Name
SXP7.92s.pdf
Description
PDF editoriale
Size
3.32 MB
Format
Adobe PDF
Checksum (MD5)
7db53c1020c5ddf0840c32aec3256180