Modelling of neutron star mergers: Fundamental atomic structure, electron-impact excitation and recombination calculations in support of collisional-radiative modelling and radiative transport.  

Supervisory team : Connor Ballance (primary supervisor), Catherine Ramsbottom (secondary supervisor) and Stuart Sim (third supervisor)

In August 2017 gravitational wave detectors found their first neutron star merger as part of the LIGO and VIRGO projects. Neutron stars come in pairs and represent ultra-dense collapsed cores of stars, they ultimately collide at 20% of the speed of light and create a radioactive expulsion of heavy elements. This new astrophysical phenomenon is termed a kilonova and was awarded Science’s Breakthrough of the year. These binary neutron star mergers are thought to be the forge in which the heavy r-process elements with atomic number great than Fe are formed. The first kilonova has provided us with rich and complex spectra and understanding these observations is the basis for understanding the physics of these events. To interpret these observations, it is necessary to simulate the physical conditions of the event via modelling.

Relativistic atomic structure and subsequent electron-impact collisions based upon these structures are the foundation of collisional radiative modelling and radiative transport models. At the expected temperatures and densities involved with kilonova modelling, electron-impact excitation and recombination would be dominant collisional processes. Although any student would be encouraged to be involved in any aspect of the modelling at QUB (or one of our collaborator sites), initially the focus would be the calculation of di-electronic recombination and radiative recombination rates using the atomic code AUTOSTRUCTURE. The next goal would be the interfacing of these rates with  the QUB radiative transport codes (TARDIS and ARTIS).

Supervision of this project would involve Cathy Ramsbottom, Connor Ballance and Stuart Sim, who are experts in the relevant atomic theory and radiation transport modelling. Funding of a student for this project is guaranteed as part of a major European Research Council grant, awarded to the project supervisors. The PhD student working on this project will therefore be expected to be part of the HEAVYMETAL international research team, a collaboration between QUB, University College Dublin, GSI Darmstadt and the University of Copenhagen. As such, applicants should expect that this project is likely to involve periods of travel and/or extended visits to our project partners.

Benefits to the Student(s)

• Excellent collaborative networks in the UK, Europe and the USA have been established to complement all three projects. The student will get the opportunity to travel and liaise with both theoretical and experimental groups in institutes around the world.
• The student will be trained in complex theoretical quantum physics and radiative transfer modelling and will get the opportunity to run some of the most sophisticated computer codes on some of the largest supercomputers in the world.
• All three projects are interdisciplinary, involving expertise in mathematics, physics, astronomy, modelling, computer science and experimental techniques. This will give the student the opportunity to gather many varied skills throughout their PhD train- ing.
• The opportunity to travel for collaborative visits, conferences and workshops will be extensive

Required skills

• Previous experience with programming would be beneficial. A large component of the project shall be computational, and an interest in developing these skills on local par- allel computing platforms and/or national/international supercomputers is required.
• A basic understanding of introductory quantum mechanics and atomic structure would also be beneficial.
• An interest in astrophysics and modelling.

For further information, please contact c.ballance@qub.ac.uk, c.ramsbottom@qub.ac.uk or s.sim@qub.ac.uk.