Giants with infrared excess.
Abstract
We have correlated optical and infrared catalogs in order to extract a large sample of luminosity class III stars with known infrared flux densities. For a non-negligible fraction of G and K giants, a far-infrared excess emission was found, starting beyond 25μm. An explanation in terms of present-day mass loss thus becomes unlikely, since the dust should then be warmer and the excess emission less far in the infrared. We believe that the far-infrared excesses of these objects, most likely first-ascent giants, are related to the Vega phenomenon. The dusty disks around these stars, gradually cooled down during their main-sequence phase, could be reheated once the star leaves the main sequence and enters the luminous post-main-sequence phase. The fairly large sample we constructed enables us to derive an estimation for the occurrence of excesses. This fraction of G or K giants with far-infrared excess appears to be distinctly smaller than among main-sequence stars. Since the higher radiation field of giants could lead to a larger evaporation rate of the circumstellar debris, this fact does not conflict with our hypothesis.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- July 1997
- Bibcode:
- 1997A&A...323..513P
- Keywords:
-
- CIRCUMSTELLAR MATTER;
- STARS: EVOLUTION;
- STARS: LATE-TYPE;
- STARS: STATISTICS;
- INFRARED: STARS