A Search for Transiting Extrasolar Planets and Variable Stars in the Galactic Plane

Abstract

This work describes the observations and results found from a photometric survey of a 0.5° by 0.5° area of the Galactic Plane performed using the 2.2 metre ESO telescope at La Silla, Chile. The dataset comprises a total of 267 images with 204 from a 16 day observation run in 2005 and 63 from a six week observation run in 2002. The new image subtraction reduction algorithm implemented on this data resulted in more than 500,000 lightcurves with a magnitude limit of R ~ 24.5. The precision of the data following reduction is suitable for transit searches as well as identification of variable stars.

Resulting from the transit search was an initial list of 31 candidates, reducing to 23 on further examination. Nine candidates were eliminated by examination of the images and the remaining list re-reduced. After this reduction three good candidates remain. These candidates have periods from 1.2840 to 2.6269 days and depths of around 75 mmags. These three candidates require followup of either multi-colour photometry or spectroscopy to determine their nature.

The variable star search resulted in detections of 1475 variable stars of different types. The largest portion were eclipsing binary stars. A number of the contact binaries have possible low mass-ratios and there are also a number of contact and detached binaries which may contain low-mass components. Three of the contact binaries were found to have periods at the known period cut off including two with periods lower than any previously published. Also identified were two possible pre-main sequence detached eclipsing binaries. The binary fraction of the field was calculated from the observed contact binaries to be 46% ± 4%. There are a number of possibilities for further data mining of the survey.