Research

My main research interest is currently active galactic nuclei (AGN), some of the most luminous objects in the universe, powered by accretion of matter on to a supermassive black hole. The spectrum is dominated by direct emission from a hard X-ray source in the hot corona around the black hole as well as reflection of this off the accretion disc.

My work aims to understand the high quality reflection spectra we have obtained with the latest generation of X-ray observatories in terms of the fundamental physics such as general relativity we know must be at work around these super massive black holes, asking what the observations are actually telling us about how these systems work.

In addition observational studies of AGN, I am developing ray tracing codes to model gravitaional light-bending around the black hole to study the effects of various properties of the X-ray source and accretion disc on the observed emission spectrum and reverberation time lags between the primary continuum and reflected radiation, providing a context in which observational results can be analysed.

I have devised a method to reconstruct the emission from each part of the accretion disc from X-ray spectra of AGN to determine the emissivity profile of the accretion disc directly through observations, that is the variation in reflected flux over the accretion disc. Comparing this as well as observed spectra and reverberation lags to systematic models produced in ray tracing simulations, I am able to constrain the location, extent and geometry of the X-ray source.

I am particularly interested in high performance computing techniques and am currently developing general relativistic raytracing codes for GPUs using the NVIDIA CUDA architecture.

Selected papers

• The origin of the lag spectra observed in AGN: Reverberation and the propagation of X-ray source fluctuations
  D.R. Wilkins and A.C. Fabian, 2012. Accepted for publication in MNRAS
• Understanding X-ray reflection emissivity profiles in AGN: Locating the X-ray source
  D.R. Wilkins and A.C. Fabian, 2012, MNRAS 424, 1284-1296
• Determination of the X-ray reflection emissivity profile of 1H 0707-495
  D.R. Wilkins and A.C. Fabian, 2011, MNRAS 414, 1269-1277
• Long XMM observation of the narrow line Seyfert 1 galaxy IRAS 13224-3809: Rapid variability, high spin and a soft lag
  A.C. Fabian, E. Kara, D. Walton, D.R. Wilkins, et. al., 2012. Accepted for publication in MNRAS
• On the determination of the spin of the black hole in Cyg X-1 from X-ray reflection spectra
  A.C. Fabian, D.R. Wilkins, J.M. Miller, R.C. Reis, C.S. Reynolds, E.M. Cackett, M.A. Nowak, G.G. Pooley, K. Pottschmidt, J.S. Sanders, R.R. Ross, J. Wilms, 2012, MNRAS 424, 217-223
• 1H0707-495 in 2011: An X-ray source within a gravitational radius of the event horizon
  A.C. Fabian, A. Zoghbi, D. Wilkins, T. Dwelly, P. Uttley, N. Schartel, G.Miniutti, L. Gallo, D. Grupe, S. Komossa, M. Santos-Lleo, 2011, MNRAS 419, 116-123
• The closest look at 1H 0707-495: X-ray reverberation lags with 1.3 Ms of data
  E. Kara, A.C. Fabian, E.M. Cackett, J. Steiner, P. Uttley, D.R. Wilkins and A. Zoghbi, 2012. Accepted for publication in MNRAS
• Testing the accuracy of radiative cooling approximations in SPH simulations
  Daniel R. Wilkins and Cathie J. Clarke, 2011, MNRAS 419, 3368-3377

Career

• 2009-present: Research student, Institute of Astronomy, University of Cambridge
• 2006-2008: Summer research student in High Energy Physics, STFC Rutherford Appleton Laboratory
• 2004: Nuffield bursary student in Space Science and Technology, CCLRC Rutherford Appleton Laboratory

Qualifications

• MSci, BA (Hons) in Natural Sciences (Experimental and Theoretical Physics), Jesus College, University of Cambridge, 2009

Awards and Prizes

• 2006-2010: Foundation scholarship, Jesus College, Cambridge
• 2008-2009: College prize in physics, Jesus College, Cambridge
• 2004: British Academy CREST (Creativity in Engineering, Science and Technology) Gold Award

Public Outreach

I have a particular interest in communicating science to the general public. I give a number of public talks on astronomy and related topics aimed at a range of audiences, particularly those with no particular background in physics or astronomy. This includes talks at the Institute of Astronomy's Public Observing Evenings as well as a number of talks to students in local schools. I am also involved in the running of these evenings and give tours and demonstrations of the historic telescopes to the public as well as school and other groups.

Professional Organisations

• Fellow, Royal Astronomical Society
• Associate Member, Institute of Physics