Main Belt Asteroid Shapes from SuperWASP Photometry

Grice, Jonathon P. (2021). Main Belt Asteroid Shapes from SuperWASP Photometry. PhD thesis The Open University.



The SuperWASP telescope was used to search for exoplanetary transits. It also serendipitously observed Solar System Objects, with a large number of main belt asteroids being observed for at least one apparition by the telescope. Data are available for the year 2004, and then from 2006 to 2012, but data collected after 2006 has remained largely unused. The large field of view of the telescope (974 square degrees) as well as the length of time the telescope has been observing has resulted in large amounts of photometry for asteroids with an apparent brightness above V = 15. In many cases, the amount of photometry for an asteroid in the SuperWASP dataset is comparable to the other photometry currently in existence for that asteroid.

This thesis describes the pipeline created to take existing SuperWASP photometry, reject observations of high photometric uncertainty and produce lightcurves suitable for shape modelling. A novel method of fitting double-sinusoids to lightcurves to quickly determine the rotational period of an asteroid is also described, and uses and limitations discussed. A total of 89 models were created for 50 asteroids, with 6 of these asteroids not previously having models. A significant difference between the existing model and model created in this work was found for 6 asteroids.

The properties of models produced in this work and previously published models are studied. It is shown that the anisotropy of asteroid spin axis longitudes is present in the sample of asteroids that have models. The relationship between spin axis longitude and other dynamical properties such as semi-major axis and argument of perihelion are explored, and it is demonstrated that the anisotropy is more prevalent for asteroids with an estimated diameter greater than 20 km.

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