Potential PhD projects: Gravitational Wave Astrophysics

Gravitational Wave Astronomy

Supervisor: Dr Christopher J. Moore (Email cmoore[at]star.sr.bham.ac.uk)

The era of gravitational wave astronomy has begun. LIGO and Virgo have unearthed the signals from several pairs of merging black holes and one pair of merging neutron stars. Many more events are expected over the next few years. These signals must be compared against detailed theoretical models to enable us to accurately determine the properties of the sources. These theoretical models will need to be significantly improved to cope with the exquisite, high signal to noise ratio , observations promised by the next generation of ground-based detectors, as well as the upcoming space-based detector, LISA. This new generation of gravitational wave instruments will pose new challenges that must be overcome in order to maximise their scientific potential. These challenges include, for example, managing very long duration signals containing many more wave cycles, avoiding confusion when analysing data sets containing multiple simultaneous overlapping signals, and efficiently combining the information from the large numbers of events to learn about the underlying astrophysical processes. This project will aim to tackle some of these future challenges whilst also working with the current LIGO and Virgo observational data.

Gravitational Waves from Binary Black Holes

Supervisor: Dr Patricia Schmidt (Email: P.Schmidt[at]bham.ac..uk)

Gravitational waves from merging black holes are a powerful tool to probe the fundamental nature of black holes and study their properties. Current measurements only allow us to place weak constraints on the mass ratio and the black hole spins. Improvements to gravitational-wave detectors will increase their sensitivity and thus also allow for more accurate measurements in the future. This require s accurate models of the gravitational-wave signal. The goal of this project is to improve the waveform models for binary black holes and to understand the consequences for Bayesian parameter estimation and tests of General Relativity in Advanced LIGO and beyond. This project will use tools and techniques from analytical relativity and provide the student with opportunity to perform targeted numerical relativity simulations of binary black hole mergers in order to further our understanding of the highly nonlinear merger of two coalescing black holes. Additionally, the successful candidate will also have opportunities to actively participate in the analysis of LIGO data.

To successfully complete this project, strong mathematical skills are required. Programming experience in Python and/or C is advantageous. Applicants must have had an introduction to General Relativity.

Studying the physics and populations of black holes and neutron stars wi th gravitational-wave observations

Supervisor: Prof Alberto Vecchio (Email: av[at]star.sr.bham.ac.uk)

Projects are available to use LIGO/Virgo data to characterise the properties of black holes and neutron stars in binary systems, and the behaviour of extreme space-times. The gravitational-wave instruments LIGO and Virgo will re-start observations at improve sensitivity in early 2019 and are expected to observe about a hundred of binary black holes and a handful of binary neutron stars in the period 2019-2022. They could also discover the first neutron star-black hole system. The project(s) will focus on characterising the physical properties of the indi vidual systems and, from those, the properties of the underlying populations. For selected systems, it may also be possible to use the gravitational-wave data to test specific predictions of general relativity.

Stellar Interactions and Transients

Supervisor: Dr Silvia Toonen (Email s.toonen[at]bham.ac.uk)

Stellar mergers mark the violent end of the life of a binary, and give rise to some of the most energetic events known in the universe; ranging from electromagnetic transients (such as supernova type Ia and luminous red novae), as well as gravitational wave sources (with LIGO & LISA). Upcoming surveys will open an unprecedented window to these events, and directly provide information on their properties. However, the exact progenitors and their formation are often unclear, and the relative importance of different types of mergers uncertain. The aim of this project is to explore the evolution self-consistently using stellar evolution modelling and population synthesis. With a computational approach, we will study not only binary evolution, but also focus on the cutting-edge field of triple evolution using innovative methods and codes. We will identify stellar mergers, compute their occurrence rate for various assumptions of stellar evolution and interaction, and finally set against the results from gravitational wave and electromagnetic surveys to unravel the mysterious progenitors of stellar mergers.

To get a feeling about the kind of research you will be doing, here are a couple of papers by Dr. Toonen relevant to this project:

For more information, please see Dr Toonen's webpage at http://www.sr.bham.ac.uk/~toonen/

Astrophysics and phenomenology of gravitational-wave sources with LIGO and LISA

Supervisor: Dr Davide Gerosa(Email d.gerosa[at]bham.ac.uk)

This project concentrates on developing theoretical and astrophysical prediction s of gravitational-wave sources.

The first observations of gravitational waves by LIGO have ushered us into the golden age of gravitational-wave discoveries. Thousands of new events are expected to be observed in the next few years as detectors reach their design sensitivities. Such large catalogs of gravitational-wave observations will open new, unprecedented opportunities in terms of both fundamental physics and astrophysics. Crucially, they will need to be faced with increasingly accurate predictions. First, among large catalogs, there will be ``golden'' events. We expect systems that, because of their properties, are particularly interesting to carry out some specific measurements (perhaps because of their favorable orientations, or because they are very massive, or very rapidly rotating, etc). Second, large catalogs need to be exploited with powerful statistical techniques. In the long run, future facilities like LISA will deliver new kinds of sources providing access to a whole new set of phenomena in both astrophysics and fundamental physics. New theoretical tools and techniques need to be developed (and immediately applied!) to maximize the scientific payoff of current and future gravitational-wave observatories.

To get a feeling about the kind of research you will be doing, here is a couple of papers by Dr. Gerosa relevant to this project:

You will have the opportunity to collaborate with numerous scientists inside and outside Birmingham. Dr. Gerosa's group has strong ties with other researchers at the Birmingham Institute for Gravitational Wave Astronomy as well as several other groups worldwide (including Johns Hopkins, Cambridge, Caltech, Dallas, Rochester, Mississippi, Milan, and Vanderbilt).

Project prerequisites: strong background in mathematical physics; solid coding s kills (python preferred); introduction to General Relativity.

For more information, feel free to contact Dr. Gerosa at d.gerosa[at]bham.ac.uk and see his webpage at https://davidegerosa.com

Project title: Characterising the optical counterparts to gravitational waves

Supervisor: Dr Matt Nicholl (Email: mnicholl[at]star.sr.bham.ac.uk)

Joint detections of gravitational and electromagnetic radiation from the same source offers a new way to study the Universe. Mergers of double neutron star binaries lead to ‘kilonovae’: a week-long glow powered by the radioactive decays from heavy nuclei forged in the explosion. This was confirmed in spectacular fashion by the first optical emission found from a gravitational wave source, GW170817. It produced a mass many times that of the Earth in gold alone, suggesting that such mergers may be the dominant production site of most heavy elements in the Universe.

The goal now is to increase our understanding of neutron star and kilonova physics by detecting and characterising more sources. As gravitational wave detectors become more sensitive over the coming years, the rate of discoveries for neutron star mergers will increase from one to 10s or more per year. The student will develop machine learning and Big Data tools to discover kilonovae and other rare events from optical observations. During LIGO’s fourth observing run, they can join the ENGRAVE collaboration to follow-up gravitational wave triggers and hunt for kilonovae with the Very Large Telescope.

An indication of the type of work to be carried out can be found here (my paper on the GW170817 kilonova): https://arxiv.org/pdf/1710.05456.pdf