Issue |
A&A
Volume 449, Number 1, April I 2006
|
|
---|---|---|
Page(s) | 313 - 326 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20053804 | |
Published online | 16 March 2006 |
New evolutionary calculations for the born again scenario
1
Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque S/N, (B1900FWA) La Plata, Argentina e-mail: [althaus;panei;mmiller]@fcaglp.unlp.edu.ar
2
Institute for Advanced Study, School of Natural Sciences, Einstein Drive, Princeton, NJ, 08540, USA e-mail: aldos@ias.edu
Received:
9
July
2005
Accepted:
4
November
2005
We present evolutionary calculations to describe the born-again scenario for post-AGB remnant stars of 0.5842 and 0.5885 . Results are based on a detailed treatment of the physical
processes responsible for the chemical abundance changes. We
considered two theories of convection: the standard mixing length
theory (MLT) and the double-diffusive GNA convection. The latter
accounts for the effect of the chemical gradient (
) in the
mixing processes and in the transport of energy. We also explore the
dependence of born-again evolution on some physical hypotheses, such
as the effect of the existence of non-zero chemical gradients, the
prescription for the velocity of the convective elements and the size
of the overshooting zones. Attention is paid to the behavior of the
born-again times and to the chemical evolution during the ingestion of
protons. We find that in our calculations born again times are
dependent on time resolution. In particular when the minimum allowed
time step is below 5
10-5 yr we obtain, with the standard
mixing length theory, born again times of 5–10 yr. This is true
without altering the prescription for the efficiency of convective
mixing during the proton ingestion. On the other hand we find that the
inclusion of chemical gradients in the calculation of the mixing
velocity tends to increase the born again times by about a factor of two. In addition we find that proton ingestion can be altered if the occurrence of overshooting is modified by the
-barrier at the H-He interface, significantly changing born again times.
Key words: stars: evolution / stars: abundances / stars: AGB and post-AGB / stars: individual: PG 1159
© ESO, 2006
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.