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Gravitational wave searches associated with galactic core-collapse supernovae

Coughlin, Scott Benjamin 2015. Gravitational wave searches associated with galactic core-collapse supernovae. MPhil Thesis, Cardiff University.
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Understanding the mechanism by which stars become supernovae is a major unsolved problem in astrophysics. They are driven by the release of gravitational energy, which is expelled largely in the form of neutrinos. After almost 40 years of numerical simulations, it is still unclear how and why large stars explode. A core-collapse supernova (CCSN) begins when its core collapses and drives a shock wave outwards. Due to the emission of neutrinos and the inward pressure of the core collapse, the shock wave briefly subsides. The mechanism for the revival of the shock wave and subsequent supernova explosion is presently unknown. Proposed mechanisms include the neutrino, magnetorotational, and the acoustic mechanisms. Gravitational Waves (GWs) will help answer how large stars explode. The violent motions of dense matter in the stars core produce GWs, and their shape is determined by that motion. Therefore, the physical processes (i.e. either the neutrino, magnetorotational, or the acoustic mechanisms) can be inferred by studying the GWs. Estimates from numerical simulations indicate that the GWs from a supernova anywhere in the Milky Way would be strong enough to be detectable by advanced LIGO. A large burst of neutrino particles is also emitted in the core collapse; together with the GWs, these can determine the location of the supernova on the sky before the shock breakout, giving astronomers a chance to see the earliest stages of the explosion. Because the Galactic supernova rate is no larger than about one every thirty years, it is necessary for a search to be ready from the beginning of the operation of advanced LIGO. This search should include the ability to detect any plausible GW polarization that could arise from a CCSN. Speci�cally, the knowledge of the precise time and sky location of the SN provided by neutrino and optical detection respectively constrains how the GW signal will appear in a network of detectors. Thus, deviations from the expected detector response could reveal if GWs contain polarizations beyond those predicted by GR. This thesis explores the ability of aLIGO to detect scalar polarizedGWs from CCSNe and other possible galactic sources.

Item Type: Thesis (MPhil)
Status: Unpublished
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: Neutrino, Magnetorotational, Acoustic mechanisms Gravitational waves, Supernovae, Advanced LIGO, CCSN
Funders: Cardiff University, International Office
Date of First Compliant Deposit: 30 March 2016
Last Modified: 10 Oct 2017 16:39

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