Chemical Abundance Analysis of Rho Puppis Stars
Abstract
Rho Puppis stars show the same chemical abundance peculiarities as the somewhat hotter metallic-line A-type (Am) stars. The abundance pattern associated with Am stars is thought to arise from chemical separation due to a lack of mixing in these stars' atmospheres. This lack of mixing has been linked to low rotational velocities and the absence of the helium ionization zone that drives both convection and a pulsational instability. The helium ionization zone is temperature dependent, and once an Am star evolves and becomes cooler than about 6500 K, the re-establishment of this zone leads to deepening surface convection which mixes the outer envelope of the star, and thus erases the chemical peculiarities. The effective temperatures of the Rho Puppis stars are sufficiently cool that the helium ionization zone should have been re-established, leading to the presence of convection, mixing, and the erasure of these chemical peculiarities. Two theories have developed to attempt to explain the peculiar abundance patterns of Rho Puppis stars. One theory is that we are seeing Am stars in a very short lived phase between the re-establishment of the helium ionization zone and the consequent erasure of chemical peculiarities. The other theory suggests that Rho Puppis stars are related to the Ba Dwarf stars in that they have gained their chemical abundance patterns via mass transfer from a once Asymptotic Giant Branch star, now turned white dwarf. I am conducting a detailed chemical abundance analysis of a number of Rho Puppis stars in an attempt to determine which, if either, of the two proposed theories explain the presence of chemical abundance peculiarities in these stars' atmospheres.
- Publication:
-
American Astronomical Society Meeting Abstracts #215
- Pub Date:
- January 2010
- Bibcode:
- 2010AAS...21542520M