2 to 20 micron observations of mass loss from early-type stars

Values are derived for the infrared wind emission for 16 O, B, and A stars by comparing observed fluxes at K, L, M, N, and Q with photospheric model atmospheres. The infrared emission is strongly correlated with the emisison of the H-alpha recombination line, in agreement with models of thermal wind emission. The bulk of the wind material must be at a temperature which is near the stellar effective temperature. A combined analysis of the infrared data and previous radio observations shows that the velocity law varies dramatically from star to star. Any mass-loss rates derived from infrared data alone are therefore highly uncertain. For two stars, 9 Sgr and Cyg OB2 No. 9, the observed radio flux cannot be thermal emission from a stellar wind.