Speaker
Description
We study Quasistars, which consist of a stellar to intermediate mass black hole embedded inside a massive star-like envelope. The accretion rate onto the black hole matches the Eddington rate for the entire Quasistar, easily placing it in the hyper-Eddington accretion region. The quick growth of the black hole leads to the outwards transport of angular momentum and energy, causing the envelope to expand following n=3 polytropic relationships. We allow the black hole to have some small initial offset from the center of mass of the Quasistar and have some initial tangential velocity, which makes the black hole orbit inside of the Quasistar. This orbit generates gravitational radiation as a result of a sinusoidal Quadrupole moment tensor that can be modeled through the use of the Quadrupole formula. We use analytical models to derive formulas for the separation between the black hole and the envelope’s center as a function of time and the characteristic gravitational wave amplitude as a function of radiation frequency. We then numerically model these formulas for various initial mass and separation conditions. The numerical model for characteristic gravitational wave amplitude can be compared to the sensitivity curves of active and upcoming gravitational wave observatories, such as LIGO, LISA, and μAres, in order to determine the detectability of the system. We find that the separation between the black hole and the envelope’s center increases over time, which is an unconventional result that stems from the nature of sub-Keplerian orbits and the mass transfer between the black hole and the envelope. Additionally, we find that our model produces gravitational waves with peak strain amplitudes between $10^{-20}$ and $10^{-24}$ at frequencies between $10^{-5}$ Hz and $10^{-9}$ Hz, which is 2 to 6 magnitudes below the sensitivity curve of μAres.
