Tidal disruptions of white dwarfs as probes for intermediate mass black holes in globular clusters

• Applicant: Professor Dr. Stephan Rosswog
• Subject Area: Astrophysics and Astronomy
• Term: from 2008 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 67273889

• Final Report Year: 2013

Final Report Abstract

Tidal disruptions of stars by massive black holes have long been recognized as a way to infer the properties of otherwise undetectable, “dormant” black holes. Within the funded project we studied the possibility to infer the existence of so-called intermediate mass black holes via tidal disruptions of white dwarf stars. It has turned out that white dwarfs of all masses may be brought to a thermonuclear explosion by the action of tidal forces from the black hole, provided that they enter deeply enough into the tidal radius of the black hole. This mechanism is viable for white dwarfs of all masses and compositions and it does not depend on the Chandrasekhar mass. It is restricted, though, to black holes with masses below ∼ 105 M , otherwise the white dwarf is swallowed as a whole. Therefore the detection of an underluminous thermonuclear supernova followed by a soft X-ray flare from the accretion of white dwarf debris can be considered as a telltale for the existence of an intermediate mass black hole. Within this project we have, on the one hand, studied such encounters using existing computational technology (Newtonian fluid dynamics together with Newtonian or pseudo-relativistic potentials and nuclear reaction networks) and we have developed new relativistic formulations of Smooth Particle Hydrodynamics in an effort towards general-relativistic (fixed Kerr-metric) models. The computational technology development begun within the framework of this project will be applied in future, relativistic tidal disruption studies.

Publications

• Astrophysical smooth particle hydrodynamics. New Astronomy Reviews, Volume 53, Issue 4-6, p. 78-104 (2009)
  S. Rosswog
  
• The star ingesting luminosity of intermediate-mass black holes in globular clusters. The Astrophysical Journal Letters, Volume 697, Issue 2, pp. L77-L80 (2009)
  E. Ramirez-Ruiz, S. Rosswog
  
• Tidal Disruption and Ignition of White Dwarfs by Moderately Massive Black Holes. The Astrophysical Journal, Volume 695, Issue 1, pp. 404-419 (2009)
  S. Rosswog, E. Ramirez-Ruiz, W.R. Hix
  
• Conservative, special-relativistic Smoothed Particle Hydrodynamics. Journal of Computational Physics, Volume 229, Issue 22, p. 8591-8612 (2010)
  S. Rosswog
  
• Relativistic Smooth Particle Hydrodynamics on a given background spacetime. Classical and Quantum Gravity, Volume 27, Issue 11, id. 114108 (2010)
  S. Rosswog
  
• Special-relativistic Smoothed Particle Hydrodynamics: a benchmark suite. Meshfree Methods for Partial Differential Equations V, Lecture Notes in Computational Science and Engineering Volume 79, pp 89-103 (2011)
  S. Rosswog