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

We present calculations indicating the possibility of a new class of Type I supernovae. In this new paradigm relativistic terms enhance the self gravity of a carbon-oxygen white dwarf as it passes or orbits near a black hole. This relativistic compression can overwhelm the tidal forces and cause the central density to exceed the threshold for pycnonuclear reactions so that a thermonuclear runaway ensues. We consider three possible environments: 1) white dwarfs orbiting a low-mass (∼ 10− 20 M⊙) black hole; 2) white dwarfs encountering a massive (∼ 1−3×103 M⊙) black hole in a dense globular cluster; and 3) white dwarfs passing a supermassive (∼ 10 − 10 M⊙) black hole in a dense galactic core. We estimate the rate at which such events could occur out to a redshift of z ≈ 1 and conclude that events involving a supermassive or massive black hole in a dense galactic core or globular cluster may be the most frequent. We estimate that the rate is sufficient to warrant a search for this class of supernova and propose several observable signatures which might be used to identify this type of event.