An Atlas of Optical Continuum and Line Emission from Low-Mass X-Ray Binaries

Shahbaz, T.; Charles, P. A.; Smale, A. P.; Naylor, T.; van Paradijs, J.; Hassall, B. J. M.; Callanan, P.
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Journal Article, Oxford Univ. Oxford, United Kingdom

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Broadband optical spectra of a sample of 15 low-mass X-ray binaries (LMXBs) is obtained in the range of 4000-9000 A. The spectra are fitted with combinations of standard accretion disc models and secondary star templates. The slope steepness relating to an optically thick accretion disc and x-ray heating of the outer parts of the disc is discussed for the sample of LMXbs in which the power-law indices of the accretion disk flux distribution were determined. Optical spectra of X1705-250, XB1905+00 and XB1916-053 are presented with optical line emission detected in most of the sample. The Balmer lines H-alpha and H-beta are found to generally be the strongest lines with mean equivalent widths of 3.7 and 1.9 A, respectively. The He(II) Lambda 4686 and the Bowen CIII/NIII blend at Lambda 4640 are also observed, with equivalent widths of 3.0 and 4.1 A, respectively. The Paschen lines are detected in Agl X-1. Theses lines are also present in Cen X-4, GS2000+25. The systems in which stellar features are detected are those in which the companions are evolved and the source in which the mass accretion rate is low.