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

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.

12 pages, 11 figures, accepted for publication in MNRAS

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Cited by in corpus (10)

• Dark spot, Spiral waves and the SW Sex behaviour: it is all about UX Ursae Majoris
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• Phase resolved spectroscopy of the accreting millisecond X-ray pulsar SAX J1808.4-3658 during the 2008 outburst
• Precision Ephemerides for Gravitational-wave Searches -- IV: Corrected and refined ephemeris for Scorpius X-1
• Time-resolved X-Shooter spectra and RXTE light curves of the ultra-compact X-ray binary candidate 4U 0614+091
• A signature of the donor star in the extra-galactic X-ray binary LMC X-2
• GX 9+9: Variability of the X-Ray Orbital Modulation
• Tomography of X-ray Nova Muscae 1991: Evidence for ongoing mass transfer and stream-disc overflow
• Gemini/GMOS Spectroscopy of EXO 0748-676 (=UY Vol) in Outburst
• New Insights into X-ray Binaries