Stability of the orbits of exoplanets

Andrew J Norton, Astronomy, started an STFC rolling grant project, linked to that of Jones/Horner, to investigate the stability of the orbits of exoplanets in hierarchical multiple stellar systems (binaries, triples, quadruple stars etc).

The code (swift_hjs) runs for millions of years of system time and each run takes several weeks of CPU time. Since the parameter space to explore is so large (different stellar masses, planetary masses, orbital separations / periods / eccentricities / inclinations and hierarchies) the project is currently open ended and likely to use a significant amount of computer time for years to come.

Andrew Norton has been using a custom-written period search program to identify all the periodic stellar variables in the SuperWASP archive. This currently contains 14 billion data points on 23 million objects. Initial period searches on subsets of objects were run on the cluster at the OU whilst the code was being developed, final runs are carried out on a similar system local to the archive itself at Leicester University.

Several papers are likely to follow reporting the half-million newly identified variable stars that the search has uncovered, but an initial study based on period-searching done at the OU is published as:
A&A 467, 785-905 (2007) ‘New periodic variable stars coincident with ROSAT sources discovered using SuperWASP’, A. J. Norton, P. J. Wheatley, R. G. West, C. A. Haswell, R. A. Street, A. Collier Cameron, D. J. Christian, W. I. Clarkson, B. Enoch, M. Gallaway, C. Hellier, K. Horne, J. Irwin, S. R. Kane, T. A. Lister, J. P. Nicholas, N. Parley, D. Pollacco, R. Ryans, I. Skillen, D. M. Wilson.

Andrew Norton & Ollie Butters run a hydrodynamical particle code - HyDisc - which simulates accretion flows in magnetic cataclysmic variable stars. There is a vast parameter space to explore (different stellar mass ratios, magnetic field strengths, orbital periods and spin periods) each of which yields a different accretion flow. Establishing flows at equilibrium requires the code to be run over many system orbital periods which can take days of CPU time.

Result are published in: The Astrophysical Journal, 672:524–530, 2008 January 1 The Accretion Flows and Evolution of Magnetic Cataclysmic Variables A. J. Norton, O. W. Butters, T. L. Parker, G. A. Wynn In an ongoing investigation we are now developing an additional code which simulates the X-ray emission that arises from each flow using a ray-tracing approach. This too requires significant cluster CPU time to calculate the simulated lightcurve for each set of system parameters.