Infrared spectroscopy of low-mass X-ray binaries - II

Using CGS4 on UKIRT, we have obtained 2.00-2.45 mu m infrared spectra of a number of low mace X-ray binaries including Sco X-l,Sco X-2 and GX13+1. Sco X-1 shows emission lines only, supporting our previous conclusion that the spectral type of the evolved secondary must be earlier than G5, Emission l ines are also seen in the spectrum of Sco X-2, confirming the identity of t he IR counterpart. We report the detection of CO bands in GX13+1, and estim ate the most likely spectral type of the secondary to be K5III. We also fin d P Cygni-type profiles in the Brackett gamma lines of Sco X-l and GX13+1, indicating the presence of high-velocity outflows in these systems, We pres ent spectra of candidate IR counterparts to several other elusive X-ray bin aries. Finally, implications for the nature and classification of these sys tems are discussed.