Disrupted Exoplanet Systems in the SuperWASP Archive

Cooper, Joseph (2020). Disrupted Exoplanet Systems in the SuperWASP Archive. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.00010f4e

Abstract

The aim of this research project has been to search for disrupted or disintegrating exoplanets; this search has been carried out using archival data from the Super-WASP (Wide Angle Search for Planets) transit photometry detection programme. The main aim of the archival search was to look for objects similar to Kepler-1520b (Rappaport et al., 2012) and Boyajian’s star (Boyajian et al., 2016), which were both discovered using the transit method of detection and both show very unusual signals when compared to a typical transiting exoplanet. The transit signal of Kepler-1520b appears to change in depth between transits, where transits have a depth between 0% and 1.3% of the flux. Boyajian’s star shows highly chaotic behaviour in the lightcurve with no distinct transit period and no consistent transit depth.

I develop bespoke routines to search the SuperWASP archive, based on the characteristics of Kepler-1520b and Boyajian’s star, to find transits that vary in depth. From these searches, objects with the largest transit depth variability were highlighted for possible follow up. The South African Large Telescope (SALT) was used to observe the spectra of four of the most interesting objects highlighted from the archive searches. These spectral observations provide stellar characteristics of the system and the subsequent WASP lightcurve analysis led to the discovery of two possible tidally disrupted transiting objects, which have been named Tidally Disrupted Transitors (TDTs) in this thesis. These objects appear to show large transit signals of up to 68% of the flux occurring frequently and in a distinct pattern for between 1-2 months. The orbital configuration of these objects also seems to suggest that they may have originated from outside the current host star’s system.

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