Developing a ground-based search system for transits of extrasolar planets

The search for extrasolar planets is a relatively new field in astronomical and astrophysical sciences that was boosted by the first discovery of the exoplanet 51 Peg b in 1995 by radial velocity measurements. The short orbital period of 4.2 days determined for this giant exoplanet encouraged the accelerated development of another search method due to the high probability that such a Hot Jupiter planet would cross its host star in the line of sight yielding a photometrically detectable signal during this crossing. This transit method (also known as the occultation or eclipse method) measures such a darkening signal as an evidence for an orbiting planet. The first detection of a transiting exoplanet HD 209458 b in 1999 and the discoveries obtained for this planet during follow-up observations demonstrated the high scientific potential of planets discovered by the transit method. The size of the exoplanet and the inclination of the orbit were determined. Combined with the information obtained with radial velocity measurements the mass and the density of the planet were calculated identifying the planet as a gas giant. Atmospheric components like Sodium, Hydrogen, Oxygen and Carbon were identified with spectroscopic measurements made with the Hubble Space Telescope. Hydrogen evaporating from the surface of the giant planet due the high stellar pressure of the nearby host star was discovered. The direct flux centered around the secondary eclipse was determined in infrared bands by measurements with the Spitzer Telescope. This unique opportunity to study detailed physical and chemical properties of exoplanets is advantageous compared to planets proven only by other search methods. In recent years only three additional transiting planets orbiting bright stars suitable for high-resolution follow-up spectroscopy have been discovered. A substantially higher number of detected transiting exoplanets are imperative to answer fundamental questions about Hot Jupiter planets. Deep surveys like OGLE (five transiting planets orbiting faint stars detected) will give higher number of detected transiting exoplanets, increasing the statistical database. Due to the faintness of the host stars the physical and chemical characterization of the detected planets will be limited. Furthermore the obtained large error estimations of the physical parameters for the planets will limit using the parameters for modeling purposes. The transit method offers the unique possibility to detect small rocky planets orbiting solarlike stars if observations are carried out from space. Satellite missions like COROT and Kepler will open this new field in the exoplanet search in the near future monitoring ten thousands of stars simultaneously from space without the disturbing noise introduced by the earth atmosphere. In this thesis the establishing of the ground-based transit survey Berlin Exoplanet Search Telescope (BEST) is described. This survey was initiated with the goal of widening knowledge about this relatively young search method for exoplanets to support the preparations for the French-led COROT satellite mission. The instrument of the search system, a 20cm Schmidt telescope, has a similar dimension as the telescope of the COROT satellite. The field of view (FOV) of BEST (3.1° x 3.1°) is comparable in size with the FOV of the COROT telescope. The set-up and the successful implementation of the BEST system are described in this work. Furthermore the developed strategies for the photometric observations, the calibration and analysis of the data, follow-up observations and their optimization are commented. Two transits of the exoplanet orbiting the star HD 209458 were already observed during the initial set-up phase of the BEST system demonstrating the feasibility that transit signals can be successfully measured with the system. During the 2-year observational campaign (2001-2003) from the Thüringer Landessternwarte (TLS) Tautenburg, Germany, three target fields were observed for 90 nights. The collected data was calibrated and analyzed by the developed automatic data