Journal Article

X-ray binary unified analysis: pulse/RV application to Vela X1: GP Velorum

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 296, issue 1, pages 33-43
Published in print May 1998 | ISSN: 0035-8711
Published online May 1998 | e-ISSN: 1365-2966 | DOI:
X-ray binary unified analysis: pulse/RV application to Vela X1: GP Velorum

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A procedure for simultaneous analysis of multiple kinds of observations is developed for binaries that contain X-ray pulsars. A wide variety of observation types might be included, although we consider only velocity: pulse and light: velocity: pulse cases at present. The model operates with equipotentials and can accommodate non-synchronous rotation and eccentric orbits. The duration condition imposed by observed X-ray eclipses is incorporated as an embedded constraint, so that only solutions consistent with the eclipse duration are found. Relations needed for the method of differential corrections in least-squares solutions are specified, and we apply the Marquardt scheme for improvement of solution convergence. Parameters of Vela X1: GP Velorum are obtained from seven combinations of pulse and radial velocity data. The estimated masses are thereby put into some perspective, especially for the neutron star. The mass of the supergiant (m sin3 i) now ranges only ±5 per cent from the mean of seven results, although the uncertainty in i makes the actual mass range larger. We discuss the determinacy of certain parameters and their historical consistency. For example, the systemic radial velocity differs among spectroscopic data sets by more than 20 km s−1. We show that, contrary to published assertions, the orbital inclinations of high-mass X-ray binaries are essentially indeterminable by the usual methods, although lower limits to inclination may be meaningful for some examples.

Keywords: techniques: radial velocities; binaries: close; binaries: spectroscopic; stars: neutron; pulsars: general

Journal Article.  0 words. 

Subjects: Astronomy and Astrophysics

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