The R Coronae Borealis stars - II. Further inferences from the infrared data
Abstract
The extensive infrared JHKL photometry of R Coronae Borealis (RCB) variables reported in Paper I is further discussed, especially in relation to the temperature and formation of circumstellar (carbon) particles. Evidence is given for a range of dust temperatures in the shell consistent with the random dust-puff model. The mean dust temperature is higher when the flux from the dust is increasing than when it is decreasing. This is also consistent with the puff model. There is no evidence from any of the stars that a significant proportion of the dust is at temperatures greater than ~1500K. It is suggested that the dust forms at ~1500K above the cool regions of large convection cells in a quasi-steady Eddington-driven outflow. Dust formation can then take place relatively close to the stellar surface, as appears necessary in order to explain the details of the RCB-type obscuration events. Enhanced C_2-band absorption seen occasionally at maximum light in RCB stars also finds a natural explanation in this model. Related data on the HdC stars are also discussed.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 1997
- DOI:
- 10.1093/mnras/285.2.339
- Bibcode:
- 1997MNRAS.285..339F
- Keywords:
-
- STARS: AGB AND POST-AGB;
- STARS: CHEMICALLY PECULIAR;
- CIRCUMSTELLAR MATTER;
- STARS: MASS-LOSS;
- STARS: VARIABLES: OTHER;
- INFRARED: STARS.