The evolution and C, N and O yields of intermediate-mass Z = 10-5 stars in isolation and in close binary systems
Document typeConference lecture
Rights accessOpen Access
We have computed the evolution of Z = 10−5 stars of masses between 4 and 9 M , from their main sequence till the late TP-(S)AGB phase.We use a recent version of the Mount Stromlo Stellar Evolution code, in which molecular opacities include the effects of variable C/O abundances ratio, . By computing hundreds (or thousands) of thermal pulses, we have been able either to remove the bulk of the stellar envelopes or to obtain stellar cores very close to MCh. Using  prescription for the mass loss rates the computed stars lose their envelopes before their cores reach MCh. This would forbid the occurrence of SN 1.5 for Z = 10−5 stars. Nevertheless the results by  suggest that the former prescription might overestimate the mass-loss rates. Therefore we have decreased the rates by . For all the cases we present, even a decrease of one order of magnitude let the stellar cores reach MCh before the envelope is lost. Therefore the occurrence of SN1.5 at Z = 10 −5 and their potential contribution to the chemical evolution of the Universe should not be discarded. We consider the combined effects of the deep/corrosive 2 nd dredge-up and Roche Lobe Overflow (RLOF) during the E-AGB to help to constrain the contribution of massive Z = 10 −5 AGB stars to the CEMPs problem. Our results have implications for the chemical evolution of the Universe and might provide another piece for the puzzle of the CEMPs problem.
CitationGil Pons, P. [et al.]. The evolution and C, N and O yields of intermediate-mass Z = 10-5 stars in isolation and in close binary systems. A: First Stars IV. "AIP Conference Proceedings". Kyoto: 2012, p. 358-360.