Ultraviolet spectroscopic variability of the WN 5 star HD 50896 - Timescales and linear physical dimensions of the perturbations

Details Ultraviolet spectroscopic variability of the WN 5 star HD 50896 - Timescales and linear physical dimensions of the perturbations Ultraviolet spectroscopic variability of the WN 5 star HD 50896 - Timescales and linear physical dimensions of the perturbations

Jan 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993a%26a...267..447s&link_type=abstract

Astronomy and Astrophysics (ISSN 0004-6361), vol. 267, no. 2, p. 447-470.

Astronomy and Astrophysics

Astronomy

26

Stellar Spectra, Stellar Winds, Variable Stars, Wolf-Rayet Stars, Line Spectra, Radial Velocity, Ultraviolet Astronomy, Ultraviolet Spectra

Scientific paper

We present the results of an analysis of a sequence of 130 high resolution SWP IUE spectra of the WN 5 star HD 50896 obtained over a period of 6 consecutive days in December 1988. Substantial variability has been found in the absorption and emission components of the major P Cygni profiles of N V 1250 A, C IV 1550 A, He II 1640 A, and N IV 1718 A as well as in a series of subordinate Fe V and Fe VI lines. The changes in the P Cygni absorption components are mainly confined to the blue edge at velocities in excess of the adopted terminal velocity of the wind and occur simultaneously for all lines. These variations take place and have a recurrence timescale of about 1 d. Variations are also found in the UV and optical (fine error sensor) light. There appears to be a correlation between the optical continuum-light and absorption component equivalent width variations; as excess absorption appears, the star becomes fainter. No genuine radial velocity variations were detected; changes in the position of various spectral features revealed by cross-correlation measurements may be entirely explained by the changing asymmetry of the line-flux distribution. We suggest that the UV spectroscopic variability of HD 50896 described here is intrinsic to the WN 5 wind and reflects changes in its physical properties. Wind models including radiative instabilities can, at least qualitatively, explain the observed variations.

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