| |
 |
| Paper: |
Evolutionary Models for AGB Stars in the Magellanic Clouds |
| Volume: |
445, Why Galaxies Care about AGB Stars II: Shining Examples and Common Inhabitants |
| Page: |
431 |
| Authors: |
Marigo, P.; Bressan, A.; Girardi, L.; Aringer, B.; Gullieuszik, M.; Groenewegen, M. A. T. |
| Abstract: |
AGB stars in the Magellanic Clouds (MCs) are the most robust calibrators
for the modelling of this phase, thanks to the large collection of
high-quality data (photometry, chemistry, pulsation properties,
mass-loss, dust features, etc.) presently available.
As part of an ambitious project aimed at substantially improving
the performance of AGB synthetic models for the MCs, we revise the
stellar models for the MCs.
Particular attention is put on the chemical composition, in terms of
both the initial mixture at the epoch of star formation, and the
subsequent changes in surface abundances during the TP-AGB phase.
We derive the initial chemical composition from recent spectroscopic
analyses, which indicate that the MCs present non-scaled-solar ratios
for key species such as C, N, O, and α–elements.
The depression of oxygen ([O/Fe] ∼ –0.2) and of nitrogen
([N/Fe] ∼ –1.0), and the rather low metallicity (Z∼ 0.005
instead of the standard Z∼ 0.008) are among the most striking
features. Evolutionary tracks are calculated with a new updated version
of the Padova stellar evolution code, from the pre-main sequence phase
up to the beginning of the TP-AGB phase, which is then decribed by means
of our synthetic model. The changes in the surface abudances (due to
the third dredge-up and hot-bottom burning) are consistenly coupled to
variations in the low-temperature opacities that are computed, for the
first time, on-the-fly with the AESOPUS code (Marigo & Aringer 2009).
Here I decribe the new sets of stellar models, with particular emphasis
on the evolution of S-type and C-type stars, as well of more massive
AGB stars experiencing hot-bottom burning. |
|
|
|
|
|
