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

Peter Anninos, P. Chris Fragile, Samuel S. Olivier, Robert Hoffman, Bhupendra Mishra, Karen Camarda
2018 Astrophysical Journal  
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 and 0.6 M_ stars on parabolic trajectories that approach 10^3 - 10^4 M_ black holes as close as a few Schwarzschild radii at periapsis, paying particular attention to the effect tidal disruption has on thermonuclear reactions and the synthesis of intermediate to heavy ion elements. These encounters create
more » ... verse thermonuclear environments characteristic of Type I supernovae and capable of producing both intermediate and heavy mass 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 β∼ 2.6 and large periapsis radius R_P ∼ 28 Schwarzschild radii. A strong inverse correlation exists between the mass ratio of calcium to iron group elements and tidal strength, with β≲ 5 producing predominately 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 ∼ 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 0.5×10^-22 - 3.5×10^-22 at 10 Mpc source distance.
doi:10.3847/1538-4357/aadad9 fatcat:a5yxwqhssbcs5frx2h2qmkoy3q