Evolutionary implications of the new triple-α nuclear reaction ratefor low mass stars

摘要

Context. Ogata et al. (2009, Progr. Theor. Phys., 122, 1055) presented a theoretical determination of the 4He(αα, γ)12C, or triple-α,nuclear reaction rate. Their rate differs from the NACRE rate by many orders of magnitude at temperatures relevant for low massstars.Aims. We explore the evolutionary implications of adopting the OKK triple-α reaction rate in low mass stars and compare the resultswith those obtained using the NACRE rate.Methods. The triple-α reaction rates are compared by following the evolution of stellar models at 1 and 1.5 M with Z = 0.0002 andZ = 0.02.Results. Results show that the OKK rate has severe consequences for the late stages of stellar evolution in low mass stars. Mostnotable is the shortening-or disappearance-of the red giant phase.Conclusions. The OKK triple-α reaction rate is incompatible with observations of extended red giant branches and He burning starsin old stellar systems.