Projected Rotational Velocities of O-Type Stars

Abstract

I present an homogeneous set of projected rotational velocities for 177 O stars based upon lUE high- dispersion spectra of the UV photo spheric lines. The line widths are estimated by cross-correlating each spectrum with the spectrum of a narrow-lined O star (HD 34078), and the widths of the cross-correlation functions are transformed to projected rotational velocity using a calibration based on the V sin i data of Conti and Ebbets. The sample includes 120 stars in common with those of Conti & Ebbets plus 57 new targets. I identify 10 stars as potential new double-lined spectroscopic binaries and 20 rapidly rotating stars as possible new line profile variables (displaying bumpy profiles associated with nonradial pulsation). There are few narrow-lined stars among the more massive and more evolved O stars, which suggests that macroturbulent broadening is important in such objects. The fastest rotators are found among the lower mass O stars, which may reflect a loss of angular momentum through stellar winds among higher mass stars.