Multi-Messenger Astrophysical Modelling of Compact Object Systems

   Department of Space & Climate Physics

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  Dr Ziri Younsi  No more applications being accepted  Funded PhD Project (Students Worldwide)

About the Project

Since the first detection of gravitational waves (GWs) from the black hole (BH) binary GW150914 by the LIGO and Virgo collaborations, a new window has been opened onto the Universe. In addition to being able to ‘see’ astrophysical phenomena using electromagnetic (EM) radiation, i.e., photons, we may now ‘listen’ for hitherto undetectable events via GWs. Over 90 GW events in the stellar-mass-range have been detected to-date, from binaries comprising BHs and neutron stars (NSs). These detections provide a unique opportunity to test gravity in the highly nonlinear and dynamical regime, providing new insights into the properties of matter and radiation under extreme physical conditions. LISA, a future spaced-based GW experiment, will transform our view of the GW Universe by detecting a plethora of new GW events, including binary supermassive BHs (SMBHs). Three years after the birth of GW astronomy, the Event Horizon Telescope (EHT) Collaboration published the first ever images of solitary SMBHs, first in M87 and later the Milky Way. These images reveal a bright emission ring enclosing the purported event horizon of the SMBH, providing new constraints on BH mass and spin, the mechanisms powering accretion and relativistic jet collimation, and even enable new tests of gravity. Modelling EM and GW emissions from compact object systems requires solving the equations of magnetohydrodynamics (MHD) for relativistic plasmas in strong gravity. In particular, the counterpart detection and characterisation of GW sources requires accurate modelling of their EM signatures. Multi-frequency EM observations from compact object systems are essential to understand their fundamental properties and governing physical processes.

The student will begin by learning to perform MHD simulations of BH accretion, calculating the multi-frequency EM emissions from the vicinity of the event horizon using covariant radiative transfer. Such calculations may be leveraged to investigate the following research directions: flaring events in the Galactic Centre, particle production and acceleration processes around BHs, and strong-field tests of gravity. The student will select one of these three directions as the focus for the first part of the project. The second part of the project will model the emission (EM and GW) from merging compact objects. The student will learn to use a numerical relativity (NR) code to simulate merging BHs (and NSs, depending on progress). The student will interface the results from their NR simulations with covariant radiative transfer, calculating contemporaneous EM and GW signal models. These models will provide new observable signatures which will help guide future LISA and EHT observations. Throughout the project the student will learn experimental techniques underpinning GW detections and Very-Long-Baseline-Interferometry (VLBI) imaging of BHs. UCL is a core member of both the LISA Consortium and the EHT Collaboration.

Desired Knowledge and Skills

  • Undergraduate or MSc in physics or astrophysics. (Required)
  • firm foundation in general relativity, radiative transfer and magnetohydrodynamics. (Required)
  • knowledge in astronomy, numerical relativity and interferometric imaging. (Desirable)
  • computational code deployment on shared and distributed memory architectures. (Desirable)
  • strong background (and demonstrable prior experience) in analytic and numerical computational approaches. (Required)
  • creativity and determination. (Required)

Entry requirements

An upper second-class Bachelor’s degree, or a second-class Bachelor’s degree together with a Master's degree from a UK university in a relevant subject, or an equivalent overseas qualification.

Additional eligibility requirements

The STFC studentship will pay your full tuition fees and a maintenance allowance for 3.5 years (subject to the PhD upgrade review).

Additional information

This project is based in the Department of Space & Climate Physics, located at the Mullard Space Science Laboratory (MSSL) in Holmbury, Surrey. MSSL is located in remote countryside in Surrey. There is limited public transport to reach the site. Before you apply to study for a PhD in our department, please check our location carefully and consider how you will regularly commute to MSSL.

How to apply

Our STFC studentships starting in September 2024 are open for applications until 26th January 2024.  

For details of how to apply please refer to our website: PhD Opportunities | UCL Department of Space and Climate Physics - UCL – University College London

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 About the Project