Optical Spectroscopy of High-Mass X-ray Binaries in the Small Magellanic Cloud
Abstract
We present results from optical spectroscopy of HMXBs in the SMC selected from Chandra and XMM-Newton surveys. We acquired 21 spectra for low-luminosity X-ray sources (Lx<10^34 erg/s), well below the typical luminosities of outbursting BeXRBs. We find that their spectral types are in the B0-B9 range, with most objects being of later types. One of them is a new Supergiant X-ray binary, the second such system identified in the SMC. Its optical counterpart is the well-known SgB[e] (and probable LBV) star S-18. With this study we raise the sample of BeXRBs with available spectral types to 52 objects. While our results are in agreement with previous studies, we find systematically later spectral types. This might be the result of extending our sample of BeXRBs to fainter sources.
- Publication:
-
X-ray Binaries. Celebrating 50 Years Since the Discovery of Sco X-1
- Pub Date:
- July 2012
- Bibcode:
- 2012xrb..confE..34M