Multiwavelength Observations of EXO 0748-676. II. Emission-Line Behavior

Pearson, K.J., Hynes, R.I., Steeghs, D., Jonker, P.G., Haswell, C.A., King, A.R., O'Brien, K., Nelemans, G. and Méndez, M. (2006) Multiwavelength Observations of EXO 0748-676. II. Emission-Line Behavior. The Astrophysical Journal, 648 (2). pp. 1169-1180. ISSN 0004-637X doi: 10.1086/506191

Abstract/Summary

We present optical and ultraviolet spectra, light curves, and Doppler tomograms of the low-mass X-ray binary EXO 0748-676. Using an extensive set of 15 emission-line tomograms, we show that, along with the usual emission from the stream and ``hot spot,'' there is extended nonaxisymmetric emission from the disk rim. Some of the emission and Hα and Hβ absorption features lend weight to the hypothesis that part of the stream overflows the disk rim and forms a two phase medium. The data are consistent with a 1.35 Msolar neutron star with a main-sequence companion and hence a mass ratio q~0.34.