White Dwarfs near Black Holes: A New Paradigm for Type I Supernovae

We present calculations indicating the possibility of a new class of Type Isupernovae. In this new paradigm relativistic terms enhance the self gravity ofa carbon-oxygen white dwarf as it passes or orbits near a black hole. Thisrelativistic compression can cause the central density to exceed the thresholdfor pycnonuclear reactions so that athermonuclear runaway ensues. We considerthree possible environments: 1) white dwarfs orbiting a low-mass black hole; 2)white dwarfs encountering a massive black hole in a dense globular cluster; and3) white dwarfs passing a supermassive black hole in a dense galactic core. Weestimate the rate at which such events could occur out to a redshift of z = 1.Event rates are estimated to be significantly less than the rate of normal TypeIa supernovae for all three classes. Nevertheless, such events may be frequentenough to warrant a search for this new class of supernova. We propose severalobservable signatures which might be used to identify this type of event andspeculate that such an event might have produced the observed"mixed-morphology" Sgr A East supernova remnant in the Galactic core.Comment: Accepted for Publication in The Astrophysical Journa