UJ Members:
Dr CA Engelbrecht (UJ group leader)
Dr C Ulusoy (postdoc)
Mr T Gülmez (PhD student)
Mr GJ Kemp (MSc student)
Mr CT Middleton (MSc student)
Mr PR Nicol (undergraduate student assistant)
Associate researchers outside UJ:
Dr FAM Frescura (senior lecturer,WITS)
Dr LA Balona (Director, South African Astronomical Observatory)
Prof RT Medupe (professor, NWU)
Dr E Olivier (Astronomer, South African Astronomical Observatory)
Dr G Handler (Research Director, Institute for Astronomy, Warsaw, Poland)
Dr E Niemczura (Wroclaw University, Poland)
Mr S Moonsamy (PhD student, WITS)
Research interests and activities:
The Asteroseismology Research Group conducts three research programmes in parallel: An observing programme, a theory programme and a time series analysis programme.
- The observing programme is focused on pulsating B and A stars of various types. In particular, we are exploring how stellar pulsations are affected by metallicity, stellar rotation and binarity respectively. We have an observing programme running at the South African Astronomical Observatory in the Northern Cape and at Boyden Observatory in the Free State. In addition, we have priority access to Kepler space telescope observations through our membership of KASC (see below).
- The theory programme has two distinct components. The first is mainly focused on exploring the description of convection, turbulence and rotation in stellar interiors. In particular, we are developing algorithms for the numerical calculation of the effects of the abovementioned physical processes on stellar structure and evolution. The aim of this work is to develop diagnostic tools for asteroseismology by calculating the effects of these processes on pulsation frequencies, amplitudes and phases.
- The other component of our theory work is focused on exploring neutron star interiors and the exterior environments of pulsars, respectively. Recent projects include a quantum-field-mechanical description of superfluid vortex arrays in neutron stars and the effects of very strong gravitational fields on pulsar radiation in a black hole – pulsar binary system.
- The programme on time series analysis is focused on exploring various approaches to time series analysis of unequally-spaced data. We run Monte Carlo simulations on the 280-node computing cluster at UJ as part of this programme.
Recent highlights:
- KASC:
Drr Engelbrecht and Ulusoy as well as Mssrs Gülmez and Middleton all joined the Kepler Asterosesimic Science Consortium (KASC) during 2010. KASC plays an essential role supporting the Kepler space telescope’s search for Earth-like planets elsewhere in our galaxy. KASC consists of approximately 400 researchers from all over the world, who use Kepler data to perform asteroseismology of unprecedented precision on the full spectrum of pulsating behaviour among stars. The remarkable precision attained by the Kepler telescope has brought noise levels in stellar photometry down from one part in ten thousand to one part in a million. The analysis of Kepler data for thousands of pulsating stars is busy “rewriting the book” on asterosesimology. The group’s first contribution to KASC output was a Monte Carlo analysis of significance levels of detected pulsation modes for the paper by Balona et al. (2011, MNRAS, ).
- Workshop on Convection in Stars:
An 8-day workshop on Convection in Stars was organised by Dr Frescura and Dr Engelbrecht, with much assistance from Prof Medupe and Dr Olivier (see the list of associate researchers above) and hosted in Council Chambers at UJ during the first two weeks of January 2011. The workshop turned out as a master class in the theory of convection and turbulence in stellar plasmas, thanks to the remarkable series of lectures prepared and delivered by uncontested luminaries in the field of stellar convection: Emeritus Professor Douglas Gough (University of Cambridge), Professor Vittorio Canuto (Columbia University and NASA Goddard Institute of Space Studies), Professor Jørgen Christensen-Dalsgaard (Århus University, Denmark) and Dr Günter Houdek (Institute for Astronomy, University of Vienna). The workshop drew 31 participants of whom 16 were students. The workshop received funding from the National Institute for Theoretical Physics (NITheP) and from WITS.
- Multisite campaign on Delta Scuti stars:
Dr Ulusoy and Mr Gülmez have organised a multisite campaign on a selection of Kepler Delta Scuti stars for July and August 2011. Observers at various locations in North America, Europe and Asia will participate in the campaign. A number of senior international astronomers will assist with the interpretation of the campaign results.