The Effect of Metallicity on the AGB Stars Evolution by Using Synthetic Model

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; 2- the mass loss rate exponentially increases with the pulsation periods; 3- The expansion velocity V AGB 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. Keyword . Stars: Evolution stars- AGB & Post AGB stars, interstellar structure, circumstellar matter, expansion velocity