Infrared Spectroscopy of GX 1+4/V2116 Ophiuchi: Evidence for a Fast Red Giant Wind?

We present infrared spectroscopy of the low-mass X-ray binary GX 1+4/V2116Oph. This symbiotic binary consists of a 2-min accretion-powered pulsar and anM5 III red giant. A strong He I 1.083 micron emission line with a pronounced PCygni profile was observed. From the blue edge of this feature, we infer anoutflow velocity of 250(50) km/s. This is an order of magnitude faster than atypical red giant wind, and we suggest that radiation from the accretion diskor the neutron star may contribute to the acceleration of the outflow. We infera wind mass loss rate of around 10^-6 Msun/yr. Accretion from such a strongstellar wind provides a plausible alternative to Roche lobe overflow forsupplying the accretion disk which powers the X-ray source. The H I Paschenbeta and He I 1.083 micron lines showed no evidence for the dramatic changespreviously reported in some optical lines, and no evidence for pulsations atthe 2-min pulsar period.Comment: 11 pages including 2 PS figures. To appear in ApJ Letter