[Previous] | [Session 45] | [Next]
K.G. Carpenter (NASA/GSFC), R.D. Robinson (IACS/CUA), G.M. Harper, P.D. Bennett, A. Brown (CASA/UCO), D.J. Mullan (Bartol/UDE)
The Goddard High Resolution Spectrograph (GHRS) on the HST has been used to acquire high-quality UV spectra of the nearby K-supergiant \lambda~Velorum. These spectra contain a wide variety of chromospheric emission lines, many of which are self-reversed by wind absorption, and thus allow us to probe the structure of both the chromosphere and wind. The observed line widths, positions, and fluxes indicate a chromosphere with a mean \log ne \approx 8.9 ± -0.2~cm-3, a turbulence (indicated by line cores with \approx~25~km~s-1 Doppler widths) greatly in excess of the photospheric value, and no general systematic flows (i.e. the wind acceleration appears to occur above the region of photon creation). We compare synthetic Fe~II line profiles from the approximate Lamers et al. (1987) Sobelev with Exact Integration (SEI) method, and from an exact comoving frame CRD calculation, with the observations. The width and shape of the wind self-absorptions implies a terminal velocity of 29--33~km~s-1, and a wind turbulence of \approx~9-21~km~s-1. We find that the wind in the 1994 GHRS observations can be described by a model with an acceleration parameter \beta~\approx~0.9 and a mass-loss rate of \approx~3~\times~10-9 M\odot~yr-1. However, this model is not consistent with the VLA 3.6~cm radio continuum flux observed in 1997.