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Nordita Astrophysics seminars

Numerical Relativity, The Einstein Toolkit, and Binary Black Mergers Inside of Stars

by Christian Ott

122:026 ()


The direct detection of gravitational waves by LIGO has opened the door to new tests of General Relativity and to true multi-messenger observations of compact objects. Numerical relativity simulations are crucial tools for predicting gravitational waves and other signals from these sources. I give an overview of numerical relativity and highlight The Einstein Toolkit, an open-source simulation toolkit for relativistic astrophysics. I discuss a recent application of the Toolkit to the simulation of binary black hole mergers in stellar-density gas. This study was motivated by the proposal that a pair of black holes could form in situ during the collapse and dynamical fragmentation of a massive star's core. The remaining gas would be accreted by the merger remnant, possibly creating outflows that could lead to an electromagnetic counterpart to a stellar-mass binary black hole merger. Our simulations show that stellar gas has a pronounced effect on the coalescence dynamics and the emitted gravitational waves, making the dynamical fragmentation proposal difficult to reconcile with the observation of GW150914.