Relativistic Tidal Disruption and Nuclear Ignition of White Dwarf Stars by Intermediate-mass Black Holes

We present results from general relativistic calculations of the tidal disruption of white dwarf stars from near encounters with intermediate-mass black holes. We follow the evolution of 0.2 M-circle dot and 0.6 M-circle dot stars on parabolic trajectories that approach 10(3) - 10(4) M-circle dot black holes as close as a few Schwarzschild radii at periapsis, paying particular attention to the effect that tidal disruption has on thermonuclear reactions and the synthesis of intermediate-mass to heavy elements. These encounters create diverse thermonuclear environments that are characteristic of Type I supernovae and capable of producing both intermediate-mass and heavy elements in arbitrary ratios, depending on the strength (or proximity) of the interaction. Nuclear ignition is triggered in all of our calculations, even at weak tidal strengths beta similar to 2.6 and large periapsis radius RP similar to 28 Schwarzschild radii. A strong inverse correlation exists between the mass ratio of calcium-group to iron-group elements and tidal strength, with beta less than or similar to 5 producing predominantly calcium-rich debris. At these moderate to weak interactions, nucleosynthesis is not especially efficient, limiting the total mass and outflows of calcium-group elements to < 15% of available nuclear fuel. Iron-group elements, however, continue to be produced in greater quantity and ratio with increasing tidal strength, peaking at similar to 60% mass conversion efficiency in our closest encounter cases. These events generate short bursts of gravitational waves with characteristic frequencies 0.1-0.7 Hz and strain amplitudes from 0.5. x. 10(-22) to 3.5. x. 10(-22) at a source distance of 10 Mpc.