Infrared observations of Be stars from 2,3 to 19,5 microns.

Spectroscopic observations of 27 Canis Majoris from 0.14 to 4.7 microns

“…The Rayleigh-Jeans approximation (ÀF x oc 1/À 3 ) has been used to extend the spectrum from the y wavelength into the infrared. From Figure 3, it can immediately be seen that the star shows an infrared excess similar to that of other Be stars, as illustrated by Gehrz, Hackwell, and Jones (1974).…”

Continuum Energy Distribution of Be Stars in the Optical Region

“…The near-ultraviolet excess emission observed in many Be stars is thought to be due to free-bound emission from the circumstellar envelope (Garrison 1978). The observed nearinfrared excess emission is due to free-bound as well as free-free emission originating from the circumstellar envelope (Gehrz et al 1974). Since the density and optical thickness of the material in the disk may vary from star to star, therefore, the strength of the excess radiation may also vary accordingly.…”

Long-term Variability in Be-Star disks

“…Using IRAS observations Waters et al (1986Waters et al ( , 1987 showed for a large sample of Be stars that the infrared flux excesses of Be stars can be understood by free-free and free-bound emission arising from the circumsteilar equatorial disk (see also Gehrz et al 1974, Kastner & Mazzali 1989. Using a simple geometry of a disk with constant opening angle and a power law radial density distribution Waters et al derived disk densities and estimated the mass-loss rates in the disk.…”

“…Assuming that the IR continuum excesses are mainly due to free-free and free-bound emission in the disk, they derived typical disk-base densities 10~1 2^, po^,lO~n gram/cm 3 (see also e.g. Gehrz et al 1974, Poeckert & Marlborough 1978, Kastner & Mazzali 1989, Johnston et al 1996. In the top panel of Figure 1 these densities are plotted as a function of spectral type.…”