Full evolutionary models for PG1159 stars. Implications for the helium-rich O(He) stars

MILLER BERTOLAMI, MARCELO M.; ALTHAUS, L. G.

ASTRONOMY AND ASTROPHYSICS

EDP Sciences

Año: 2006 vol. 454 p. 845 - 854

0004-6361

We present full evolutionary calculations appropriate to post-AGB PG 1159 stars for a wide range of stellar masses.We take into account the complete evolutionary stages of PG 1159 progenitors starting from the Zero Age Main Sequence. We consider the two kinds of Born Again Scenarios, the very late thermal pulse (VLTP) and the late thermal pulse (LTP), that give rise to hydrogen-deficient compositions. The location of our PG 1159 tracks in the effective temperature-gravity diagram and their comparison with previous calculations are discussed. Our results reinforce the idea that different abundance of 14N observed at the surface of those PG1159 with undetected hydrogen is an indication that their progenitors would have evolved through a VLTP episode or LTP. We derive new values for the spectroscopical masses based on these new models. Finally, we discuss an evolutionary scenario that could explain the existence ofPG1159 stars with unusually high helium abundances and a possible evolutionary connection between these stars and the los mass O(He) stars.