Gravitational Wave and X-ray Signals from Stellar Disruption by a Massive Black Hole

Abstract

Gravitational waves and X-ray flares are expected from tidal disruption of stars by a massive black hole. Using a relativistic smoothed particle hydrodynamics code, we investigate the fate of main sequence and Helium stars in plunge orbits passing near Schwarzschild or a Kerr black holes of 10^5-6 Msun. We show that quadrupole gravitational waves emitted during the tidal disruption process are described reasonable well by a point particle approximation even in the strong encounter case. An additional hydrodynamic calculation based on the Godunov method indicates that shocks develop for sufficiently high tidal compressions. The shock-heating results in an X-ray flare, which for solar-type stars disrupted by 10^6Msun black holes is in the keV range, associated with the gravitational wave signal. The hardness and duration of the X-ray flare may serve as a diagnostic of the mass of the central black hole.