Research and development of ground-based transiting extrasolar planet projects

• Main Author: Bento, Joao Paulo da Silva
• Published: University of Warwick 2012
• Subjects: 530; QB Astronomy
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.572923

The search for exoplanets has gone from the realm of speculation to being one of the most prolific topics of modern astronomy in the space of just 20 years. In particular, the geometric alignment of transiting exoplanets provides the added opportunity to measure a host of properties of these systems, including studies of planetary atmospheres. The vast majority of known transiting exoplanets to date were found using dedicated ground-based surveys such as the SuperWASP project. Such enterprises comprise of multiple small telescopes designed to perform high-precision photometry over a wide field of view and rely on efficiently compensating for several noise contributions. An analysis of the sources of noise in the SuperWASP light curves was performed, focussing on systematic e↵ects fixed in detector space. A study of a set of detector maps produced from the average of the fractional residuals of the light curves in CCD coordinates has revealed that the current flat-fielding strategy is introducing a component of red noise into the light curves due to the wavelengthdependent nature of the CCDs. The possibility of using such maps as a basis for an additional decorrelation step in the software pipeline is discussed. The next phase in planetary discoveries from ground-based surveys consists of the search for smaller planets and those in longer orbits around their host stars. This process involves an observing strategy that focuses on intensive coverage of particular locations of the sky. We develop simulation software to aid the choice of observed fields for the SuperWASP and Next Generation Transit Survey (NGTS) projects in order to maximise the chances of finding planets at those locations. Moreover, this simulation can be used for comparative studies of the planet finding probability for several design choices and has been used to justify the necessity to commission the NGTS instrument at ESO’s Paranal Observatory in order to benefit from one of the World’s premier sites. The increasing number of known transiting planets has triggered a new phase of exoplanet exploration, in which the properties of the atmospheres of these planets are being explored using techniques such as transmission spectroscopy. This process consists of measuring an enhanced transit depth at particular wavelengths due to the presence of opacity sources in the atmospheres of exoplanets. We use the multiband photometer ULTRACAM to attempt a similar measurement via the technique of transmission photometry for the highly inflated planets WASP-15b and WASP- 17b. The data are found to be dominated by systematic errors and a detailed study of the possible sources is performed.