The class of Jsolated stars and luminous planetary nebulae in old stellar populations

Abstract

We suggest that stars whose angular momentum (J) does not increase by a companion, star, or planet, along their post-main sequence evolution have much lower mass-loss rates along their giant branches. Their classification to a separate group can bring insight on their late evolution stages. We here term these Jsolated stars. We argue that themass-loss rate of Jsolated stars is poorly determined because the mass-loss rate expressions on the giant branches are empirically based on samples containing stars that experience strong binary interaction, with stellar or sub-stellar companions, e.g. planetary nebula (PN) progenitors. We use our earlier claim for a low mass-loss rate of asymptotic giant branch (AGB) stars that are not spun up by a stellar or substellar companion to show that we can account for the enigmatic finding that the brightest PNe in old stellar populations reach the same luminosity as the brightest PNe in young populations. It is quite likely that the best solution to the existence of bright PNe in old stellar populations is the combination of higher AGB luminosities, as obtained in some new stellar models, and the lower mass-loss rates invoked here.