Evidencia observacional acerca de la pérdida de masa en gigantes rojas de agregados estelares

J.J. CLARIÁ

San Juan

Congreso; Reunión Anual 25 de la Asociación Argentina de Astronomía; 1979

Asociación Argentina de Astronomía

Iron abundances, surface gravities, effective temperatures and masses of 14 red giants and 16 stars of the giant branch clump in three old open clusters have been determined from DDO photometry. The masses derived for stars in the post-helium flash stages of evolution are systematically lower than those found for the pre-helium flash red giants, the average difference in log (mass/solar mass) being -0.44. A second result is that the masses of the clump stars are smaller than the corresponding tornoff point masses. A similar trend between the giants and horzontal branch stars in five globular clusters as well as in the evolved stars of M67 and NGC 7789 has been found from existing DDO photometry. These results are interpreted as demonstrating that the post-helium flash stars undergo mass loss before reaching their helium core burning phase of evolution. We identify the highest luminosity phase of red giant as that during which mass is lost mos rapidly.