Ultraviolet and infrared studies of Be stars

From a comparison of ultraviolet and infrared observations of Be and normal B stars, the author finds the region producing C IV absorption in Be stars is confined in latitude to near the equatorial plane and possibly confined in radial extent close to the star. The C IV-producing region in Be stars appears to be about four times hotter than that in normal B stars of the same spectral type, implying that another mechanism must be active in Be stars in addition to radiatively-driven winds. She also finds that infrared and optical polarization data can be used to deconvolve rotation velocities and inclination angles for Be stars. The statistical correlations which led to these conclusions are based on data obtained with the IUE and IRAS satellites. She finds that C IV absorption equivalent widths in Be stars are significantly larger than those in normal B stars. C IV equivalent widths and edge velocities correlate with those of Si IV. C IV excess equivalent widths, defined as log(WBe/WNormal), correlate with 1/Teff and with inclination angle, but not with rotation velocity, luminosity class, or 12 μm excesses. Stars with lower Teff or larger inclination angle show more excess C IV absorption. C IV edge velocities show similar correlations. 12μm excesses correlate with temperature and with rotation velocity, but not with inclination angle, luminosity class, or C IV excess. Hotter stars, or those with higher rotation velocities, tend to have larger 12 μm excesses. Both the C IV excess absorption and 12 μm excess seem to turn on at a rotation velocity of 150 km s-1