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arXiv · 0707.0449

Optical spectroscopy of the low mass X-ray binary GX9+9

R. Cornelisse·D. Steeghs·J. Casares·P. A. Charles·A. D. Barnes·R. I. Hynes·K. O'Brien
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Abstract

Phase-resolved medium resolution VLT spectroscopy of the low mass X-ray binary GX9+9 has revealed narrow CIII emission lines that move in phase relative to our new estimate of the ephemeris, and show a velocity amplitude of 230+/-35 km/s. We identify the origin of these lines as coming from the surface of the donor star, thereby providing the first estimate of the mass function of f(M_1)>=0.22M_sun. Rotational broadening estimates together with assumptions for the mass donor give 0.07<q<0.35 and 182<K_2<406 km/s. Despite a low mass ratio, there is no evidence for a superhump in our dataset. Doppler maps of GX9+9 show the presence of a stream overflow, either in the form of material flowing downward along the accretion disk rim or in a similar fashion as occurs in high mass transfer rate cataclysmic variables known as the SW Sex stars. Finally we note that the Bowen region in GX9+9 is dominated by CIII instead of NIII emission as has been the case for most other X-ray binaries.

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R. Cornelisse, D. Steeghs, J. Casares, P. A. Charles, A. D. Barnes, R. I. Hynes, K. O'Brien. 2007-07-03. Optical spectroscopy of the low mass X-ray binary GX9+9. https://doi.org/10.1111/j.1365-2966.2007.12193.x

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