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Astrophysical inference from pulsar timing array searches for gravitational waves

Middleton, Hannah Rose (2018)
Ph.D. thesis, University of Birmingham.

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Gravitational waves (GWs) have been detected for the first time in 2015 by the LIGO-Virgo Scientific Collaboration. The source of the GWs was a binary black hole (BBH). The observation caught the final fraction of a second as the two black holes spiralled together and merged. This observation (and the others to follow) marked the beginnings of GW astronomy, ‘a new window on the dark universe’, providing a means to observe astronomical phenomena which may be completely inaccessible via other avenues as well as a new testing ground for Einstein’s theory of general relativity (GR). However, this is just the beginning – like electromagnetic astrophysics, there is a full spectrum of GW frequencies to explore.

At very low frequencies, pulsar timing arrays (PTAs) are being used to search for the GW background from the merging population of massive black hole binaries (MBHBs). No detection has yet been made, but upper limits have been placed. Here we present results on what inference on the MBHB population can be learnt from present and possible future PTA results, and also compare current upper limits with astrophysical predictions, finding them to be fully consistent so far.

We also present a generic method for testing the consistency of a theory against experimental evidence in the situation where there is no strong viable alternative (for example GR). We apply this to BBH observations, finding them to be fully consistent with GR and also to Newton’s constant of gravitation, where there is considerable inconsistency between measurements.

Type of Work:Ph.D. thesis.
Supervisor(s):Vecchio, Alberto and Sesana, Alberto
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Physics and Astronomy
Additional Information:

Publications resulting from research:

H. Middleton, W. Del Pozzo, W. M. Farr, A. Sesana, and A. Vecchio. Astrophysical
constraints on massive black hole binary evolution from pulsar timing arrays. MNRAS,
455:L72–L76, January 2016.

S. Chen, H. Middleton, A. Sesana, W. Del Pozzo, and A. Vecchio. Probing the assembly
history and dynamical evolution of massive black hole binaries with pulsar timing
arrays. MNRAS, 468:404–417, June 2017a.

S. Chen, A. Sesana, and W. Del Pozzo. Efficient computation of the gravitational wave
spectrum emitted by eccentric massive black hole binaries in stellar environments.
MNRAS, 470:1738–1749, September 2017c.

Subjects:QB Astronomy
QC Physics
Institution:University of Birmingham
ID Code:8044
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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