OBSERVATIONAL PROSPECTS FOR MASSIVE STARS WITH DEGENERATE NEUTRON CORES

In this paper we present observable characteristics of massive stars with degenerate neutron cores, or Thorne-Zytkow objects, which would distinguish them from other stars. Spectroscopically these stars are red supergiants, but they have peculiar surface abundances compared with ''normal'' red supergiants. This is due to the convection of rp-process products from the nuclear burning region to the surface. We present predictions of surface abundances of elements heavier than iron. In particular, Mo should have an abundance greater than 1000 times solar. We estimate that several of the approximately 100 red supergiants within 5 kpc of the Sun are Thorne-Zytkow objects.