AAS 201st Meeting, January, 2003
Session 54. Compact X-Ray Sources
Poster, Tuesday, January 7, 2003, 9:20am-6:30pm, Exhibit Hall AB

## [54.07] Spectroscopic Identification of the Infrared Counterpart to GX5-1

R. M. Bandyopadhyay (University of Oxford), T. Shahbaz (Instituto de Astrofisica de Canarias), P. A. Charles (University of Southampton)

Using CGS4 on UKIRT, we have obtained a 1.95-2.45 micron infrared spectrum of the primary candidate counterpart to the bright Z low-mass X-ray binary (LMXB) GX5-1. IR photometry by Naylor, Charles, & Longmore (1992) and the astrometry of Jonker et al. (2000) had previously identified this star as the most likely counterpart to GX5-1. The spectrum presented here clearly shows Brackett \gamma and He lines in emission, for the first time confirming the identity of the counterpart. Similar to our previous spectroscopy of the Z LMXBs Sco X-1 and Sco X-2 (Bandyopadhyay et al. 1999), the K-band spectrum of GX5-1 shows emission lines only, possibly indicating that the spectral type of the mass donor is earlier than G5. We discuss the implications of this spectrum for the nature of the Z LMXBs.