The Dynamics of White Dwarfs, Black Holes and Stellar Cusps

Citation

Wegg, Christopher (2013) The Dynamics of White Dwarfs, Black Holes and Stellar Cusps. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/YCAT-ES15. https://resolver.caltech.edu/CaltechTHESIS:08152012-212758368

Abstract

This thesis contains topics related mostly to the dynamics of white dwarfs (chapter 2), the dynamics of stars around binary super massive black holes (chapters 4, 5 and 6) and dynamics in the singular isothermal sphere (chapter 7).

In chapter 2 the kinematics of young (< 3x10⁸yr) galactic white dwarfs are investigated. A relationship between the mass and kinematics of white dwarfs is demonstrated, whereby high- mass white dwarfs have low velocity dispersion. This is the result of less scattering during the shorter lifetime of their more massive precursors. The kinematics of the highest-mass white dwarfs (> 0.95 Msun) are also investigated, and it is shown that they are consistent with the majority being formed via single-star evolution from massive progenitor stars.

In chapter 3 it is shown that the coolest, oldest white dwarfs can be identified photometrically from their unique colors, and five new ultracool white dwarfs are spectroscopically confirmed.

In chapter 4 it is shown that close binary supermassive black holes (SMBHs) should produce a burst of tidal disruptions of up to 0.1 yr⁻¹ as they form. The quiescent rate is ~10⁻⁵ yr⁻¹ per galaxy, and it is therefore shown that binary SMBHs can potentially be identified via multiple tidal disruptions from the same system.

In chapter 5 we perform more extensive simulations of the dynamics of stars around binary SMBHs to better quantify and understand the stellar dynamics. By incorporating general relativistic corrections, we also investigate the processes undergone by compact remnants orbiting the binary SMBHs, analyzing both objects that plunge directly into the SMBHs, and those that undergo extreme mass ratio inspirals (EMRIs). The potential used to mimic general relativistic precession in these simulations is novel, and more accurate for the type of nearly parabolic orbits considered in this work: It is described in chapter 6.

In chapter 7 an analytic solution to the manner in which stars diffuse in the background of a singular isothermal sphere is developed. It is shown a self-similar solution should exist, and this solution is found.

Thesis Files