The nature of infrared excesses in extreme Be stars.
Abstract
Newly measured energy distributions from 0.32-3.5 for all the extreme Be stars around Per show an infrared excess beginning at 0.5 , peaking shortward of 1 , and declining at longer wavelengths. This excess is not likely to be thermal radiation from dust, but appears to be continuum radiation from the free-bound electron interaction with neutral hydrogen. The emission presumably originates in a large gas shell around the extreme Be stars. The H-R diagrams for four clusters containing extreme Be stars are consistent with the hypothesis that the extreme Be stars are in the core-contraction stage of post-main-sequence evolution, following exhaustion of hydrogen in their convective cores. The possible role of resonance absorption in providing pressure support for the very large extreme Be star shells is noted. The eight extreme Be stars observed to date are found to have continuous or nearly continuous energy distributions across the Balmer jump. None appears to have a Balmer discontinuity in emission. One star varied by 0.3 mag at 1.6 and 2.2 , and a second appears to have varied by 0.1 mag, on a time scale of 1 year. Subject headings: Be stars - circumstellar shells - infrared
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1974
- DOI:
- 10.1086/152848
- Bibcode:
- 1974ApJ...190...73S