The stars of the galactic center

Abstract

We consider the origin of the so-called S stars orbiting the supermassive black hole at the very center of the Galaxy. These are usually assumed to be massive main-sequence stars. We argue instead that they are the remnants of low-to-intermediate mass red giants which have been scattered on to near-radial orbits and tidally stripped as they approach the central black hole. Such stars retain only low-mass envelopes and thus have high effective temperatures. Our picture simultaneously explains why S stars have tightly-bound orbits, and the observed depletion of red giants in the very center of the Galaxy.