Spectroscopy of HD 77581 and the mass of Vela X-1

Details Spectroscopy of HD 77581 and the mass of Vela X-1 Spectroscopy of HD 77581 and the mass of Vela X-1

1995-05-16

arxiv.org/abs/astro-ph/9505070v1

Astron. Astroph. 303, 483 (1995)

Astronomy and Astrophysics

Astrophysics

14 pages, incl. 7 out of 8 figures, of compressed, uuencoded postscript. Accepted for publication in A&A. For 8th figure (1Mby

Scientific paper

We present new high-resolution, high signal-to-noise optical spectra of HD 77581, the optical counterpart of the X-ray source Vela X-1, and determine radial velocities from these spectra, as well as from high-resolution IUE spectra and from digitized photographic spectra. The measured velocities show strong deviations from a pure Keplerian radial-velocity curve, which are autocorrelated within one night, but not from one night to another. Since lines of different ions exhibit very similar changes in profile, these deviations most likely reflect large-scale motions of the stellar surface akin to non-radial pulsations. A possible cause could be that the varying tidal force exerted by the neutron star in its eccentric orbit excites high-order pulsation modes in the optical star which interfere constructively for short time intervals. The effect of such velocity excursions on the orbital solution is estimated by means of a Monte-Carlo simulation technique. We investigate sources of systematic error, due to, e.g., the tidal deformation of the star, and find, in particular, evidence for a systematic perturbation of the radial velocity near the time of velocity minimum. This possible distortion severely compromises the accuracy of the radial-velocity amplitude, leading to a 95\% confidence range of 18.0--28.2\,\kms. The corresponding 95\% confidence limits of the masses are given by $\MX=1.9_{-0.5}^{+0.7}\,\Msun$ and $\Mopt=23.5_{-1.5}^{+2.2}\,\Msun$.

Affiliated with

Also associated with

No associations

Rating

Spectroscopy of HD 77581 and the mass of Vela X-1 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Spectroscopy of HD 77581 and the mass of Vela X-1, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Spectroscopy of HD 77581 and the mass of Vela X-1 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-588429