Searching for transits in the Wide Field Camera Transit Survey with difference-imaging light curves

• Published in: Astronomy and astrophysics (Berlin) 2013-12, Vol.560, p.np-np
• Main Authors: Zendejas Dominguez, J., Koppenhoefer, J., Saglia, R. P., Birkby, J. L., Hodgkin, S. T., Kovács, G., Pinfield, D. J., Sipőcz, B., Barrado, D., Bender, R., del Burgo, C., Cappetta, M., Martín, E. L., Nefs, S. V., Riffeser, A., Steele, P.
• Format: Article
• Language: English
• Subjects: Astronomy; Data reduction; Extrasolar planets; Field cameras; methods: data analysis; Photometry; Pipelines; planets and satellites: detection; Searching; techniques: photometric; Transits
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361/201321317

The Wide Field Camera Transit Survey is a pioneer program aiming at for searching extra-solar planets in the near-infrared. The images from the survey are processed by a data reduction pipeline, which uses aperture photometry to construct the light curves. We produce an alternative set of light curves using the difference-imaging method for the most complete field in the survey and carry out a quantitative comparison between the photometric precision achieved with both methods. The results show that difference-photometry light curves present an important improvement for stars with J > 16. We report an implementation on the box-fitting transit detection algorithm, which performs a trapezoid-fit to the folded light curve, providing more accurate results than the box-fitting model. We describe and optimize a set of selection criteria to search for transit candidates, including the V-shape parameter calculated by our detection algorithm. The optimized selection criteria are applied to the aperture photometry and difference-imaging light curves, resulting in the automatic detection of the best 200 transit candidates from a sample of ~475 000 sources. We carry out a detailed analysis in the 18 best detections and classify them as transiting planet and eclipsing binary candidates. We present one planet candidate orbiting a late G-type star. No planet candidate around M-stars has been found, confirming the null detection hypothesis and upper limits on the occurrence rate of short-period giant planets around M-dwarfs presented in a prior study. We extend the search for transiting planets to stars with J ≤ 18, which enables us to set a stricter upper limit of 1.1%. Furthermore, we present the detection of five faint extremely-short period eclipsing binaries and three M-dwarf/M-dwarf binary candidates. The detections demonstrate the benefits of using the difference-imaging light curves, especially when going to fainter magnitudes.