The Effect of Metallicity on the AGB Stars Evolution by Using SyntheticModel

Behaa  Chiad; Nathera  Ali; Sundus  Abdullah; Mohammed  Salih

doi:10.24996/ijs.2012.53.4Appendix.%g

Authors

Behaa Chiad Department of Physics- College of Sciences - University of Baghdad,
Nathera Ali Department of Physics- College of Sciences - University of Baghdad,
Sundus Abdullah Department of Astronomy- College of Sciences-University of Baghdad
Mohammed Salih Minstery of electricity-Iraq

DOI:

https://doi.org/10.24996/ijs.2012.53.4Appendix.%25g

Keywords:

Stars: Evolution stars- AGB & Post AGB stars, , interstellar structure, circumstellar matter, , expansion velocity

Abstract

Stars whose initial masses are between (0.89 - 8.0) M☉ go through an
Asymptotic Giant Branch (AGB) phase at the end of their life. Which have been
evolved from the main sequence phase through Asymptotic Giant Branch (AGB).
The calculations were done by adopted Synthetic Model showed the following
results: 1- Mass loss on the AGB phase consists of two phases for period (P <500)
days and for (P>500) days; 2- the mass loss rate exponentially increases with the
pulsation periods; 3- The expansion velocity VAGB for our stars are calculated
according to the three assumptions; 4- the terminal velocity depends on several
factors likes metallicity and luminosity. The calculations indicated that a super wind
phase (S.W) developed on the AGB phases, operates only during the latter part of
the quiescent phase. The results indicate that the time scale of mass loss depends on
the metallicitiy of stars and mass core.