Seeing and Hearing Massive Black Holes Feeding on White Dwarfs
Physical and Biological Sciences
Physics (Astrophysics)
Massive black holes are observationally unconstrained. In general, black holes can be detected by observing radiation from in-falling gas that shines with a peak luminosity dependent on the mass of the black hole. Dim, stellar-mass black holes fed by gas from companion stars have been detected through out the Milky Way and in nearby galaxies, and luminous super-massive black holes fed by central gas have been detected in galactic centers out to cosmological distances. Massive black holes are thought to reside in dwarf galaxy centers. But local dwarf galaxies are devoid of the gas necessary to illuminate their central black holes, and massive black holes are not luminous enough to be seen at cosmological distances where gas is abundant. To detect these elusive massive black holes, we must look for evidence of them snacking on passing stars in a process known as a tidal disruption, which happens about 10 times per year per cubic gigaparsec, a volume of space about a ten-thousandth that of our observable universe. The most luminous disruption signatures from massive black holes come from them feeding on white dwarfs, the stellar remnants of low-mass stars, and the shape of a signature depends on whether a white dwarf is disrupted from a parabolic, eccentric, or circular orbit. In this thesis I investigate the distribution of orbits a white dwarf could have when tidally disrupted by a massive black hole. I find the most likely disruption comes from a white dwarf torn from a binary stellar companion and digested by the massive black hole while in a nearly parabolic orbit, though some may be disrupted from eccentric orbits, and none would be disrupted from circular orbits. The latter case has significant implications toward current efforts to detect gravitational radiation by listening for white dwarfs orbiting massive black holes.
