A Supersoft X-Ray Binary in the Small Magellanic Cloud
Abstract
Photometric observations of the supersoft x-ray source 1E 0035.4-7230 obtained during two years reveal that the very blue optical counterpart (V_max_ = 20.2, B - V= -0.15, U - B=- 1.06) undergoes nearly sinusoidal variations with a period of 0.1719256 days and an amplitude of {DELTA}V~ 0.3 mag. ROSAT observations show the x rays vary with approximately the same period. However, either the x-ray minimum precedes the optical minimum by about a quarter cycle or there is a small period difference between the two wavelength regions. We consider that this x-ray source is a close binary, with the optical light coming primarily from an accretion disk surrounding the compact star. Optical spectra show weak, variable He II (4686 A) emission which probably originates in this disk. Possible interpretations of the light curve are discussed, including x-ray heating of the secondary star. The very broad minimum in the x-ray light curve suggests the x rays may be scattered in a large accretion disk corona (ADC) which is partially occulted, probably by an azimuthally irregular bulge on the disk rim. If this system lies at the distance of the Small Magellanic Cloud, it radiates near the Eddington luminosity.
- Publication:
-
The Astronomical Journal
- Pub Date:
- February 1996
- DOI:
- 10.1086/117824
- arXiv:
- arXiv:astro-ph/9512012
- Bibcode:
- 1996AJ....111..788S
- Keywords:
-
- X-RAYS: STARS;
- BINARIES: CLOSE;
- CATACLYSMIC VARIABLES;
- Astrophysics
- E-Print:
- 10 pages, 1 table and 3 (of 4) figures as uuencoded compressed Postscript. Also available at http://www.dao.nrc.ca/DAO/SCIENCE/science.html