Computer Science
Scientific paper
Jul 1984
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1984iue..prop.1897s&link_type=abstract
IUE Proposal ID #OBGGS
Computer Science
Scientific paper
Discrepancies in spectral line widths between UV and visual wavelength regions occur in some early-type stars with large Vsin i. The UV lines are up to a factor of two narrower than expected from visual lines, implying a lower projected rotational velocity. One interpretation suggests that the narrower UV lines originate in the hotter, more slowly rotating (i.e. polar) regions of a rapidly rotating star. If so, the line width discrepancy seen in Be stars should occur in non-emission B stars as well. Our recent IUE observations of early-type B stars show that this effect is present in non-emission stars but the UV lines are only 10-20% narrower than their visual counterparts. This result has two important implications: (1) The larger effect seen in some Be stars may be related to the Be phenomenon, and (2) The fact that there is a wavelength dependence to spectral line widths in rapidly rotating, non-emission B stars may prove to be the basis of a method to determine inclination angles and equatorial velocities. The observations of B2-B3 stars referred to above were obtained in August 1983 as part of our program to study this effect. In light of these results we now propose to extend that work to later types and complete the B star main sequence. The data are needed to determine the variation in UV photospheric line widths as a function of v sin i and spectral type, and to provide a homogeneous set of UV line profiles for comparison with our high-resolution visual spectra of the same stars. The stars we will study are all rotational velocity standard stars defined by Slettebak et al. (1975).
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