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Measuring the Mass Ratios of X-Ray Transients from the Rotational Broadening of the Secondary Star's Spectrum

Published online by Cambridge University Press:  22 February 2018

Edward L. Robinson  and
Martin Bitner
Edward L. Robinson
Affiliation:
Dept. of Astronomy, Univ. of Texas, 1 University Station, C1400, Austin, TX 78712USA (elr@astro.as.utexas.edu)
Martin Bitner
Affiliation:
Dept. of Astronomy, Univ. of Texas, 1 University Station, C1400, Austin, TX 78712USA (elr@astro.as.utexas.edu)

Extract

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We describe a new computer program for calculating the spectra of stars that fill their Roche lobes in close binary stars.

Soft X-ray Transients (SXTs) are interacting binary stars in which a compact star is stripping mass from a relatively-normal companion star (the secondary star). One step in the usual method for measuring the mass of the compact stars in these systems is to determine the mass ratio from the rotational broadening of the absorption lines in the spectrum of the secondary. With a few outstanding exceptions (e.g., Shahbaz 2003), the observations have typically been analyzed assuming that the observed spectrum can be modeled by convolving the spectrum of a non-rotating star with a line-broadening function appropriate for a rotating, spherical star. The results are often inadequate because 1) the profiles of the absorption lines vary strongly with orbital phase, and 2) the limb darkening differs from line to line so that no single broadening function can represent the behavior of all lines.

Type
The Contributed Papers
Information
International Astronomical Union Colloquium , Volume 194: Compact binaries in the galaxy and beyond , 2004 , pp. 207
Copyright
Copyright © Instituto de astronomia/revista mexicana de astronomίa y astrofίsica 2004

References

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