Physical Sciences and Mathematics Commons^™

Infrared Spectroscopy Of Symbiotic Stars. Iv. V2116 Ophiuchi/Gx 1+4, The Neutron Star Symbiotic, Kenneth H. Hinkle, Francis C. Fekel, Richard R. Joyce, Peter R. Wood, Verne V. Smith, Thomas Lebzelter

Information Systems and Engineering Management Research Publications

We have computed, using 17 infrared radial velocities, the first set of orbital elements for the M giant in the symbiotic binary V2116 Ophiuchi. The giant's companion is a neutron star, the bright X-ray source GX 1+4. We rule out the previously proposed period of 304 days and instead find an orbital period of 1161 days, by far the longest of any known X-ray binary. The orbit has a modest eccentricity of 0.10, with an orbital circularization time of ≲5 × 106 yr. The large mass function of the orbit significantly restricts the mass of the M giant. Adopting a …