Analysis of ultraviolet atmospheric eclipses in the Wolf-Rayet binaryCV Serpentis.

Abstract

The authors have obtained ultraviolet spectra covering one-half of an orbital cycle of CV Ser. Marked phase effects have been detected in which ultraviolet absorption lines are greatly strengthened when the W-R star is in front. No eclipses are seen longward of 2300 Å, while below 2000 Å blanketing by numerous lines, spread out in frequency by the velocity dispersion through the atmosphere, cause pronounced atmospheric eclipses of the O8 star. It is shown that there is considerable flux being carried in emission lines shortward of the Lyman limit. This seems to be inconsistent with photospheric effective temperatures near 30,000K. The terminal velocity of the wind, measured by using the blue edges of the Si IV and C IV resonance lines, is 3000±170 km s^-1.