Models for Nuclei of Planetary Nebulae and for Ultraviolet Stars

Abstract

A series of stellar models were evolved, all with a total mass of 0.65 M_⊙, an initial carbon-oxygen core of mass 0.60 M_⊙, an intermediate helium mantle and an outer hydrogen-rich envelope with mass varying from case to case. Although the most hydrogen-rich cases resulted in red giants, cases with ≲ 0.01 M_⊙ in the hydrogen envelope evolved at high surface temperature. The early stages of development of these models are similar to observed central stars of planetary nebulae. The later stages (when the nebula should be very thin optically) still have a high luminosity; the relevance to ‘ultraviolet stars’ will be discussed.