A hot Jupiter transiting a mid-K dwarf found in the pre-OmegaCam Transit Survey

We describe the pre-OmegaTranS project, a deep survey for transiting extra-solar planets in the Carina region of the Galactic disc. In 2006-2008, we observed a single dense stellar field with a very high cadence of similar to 2 min using the European Southern Observatory Wide Field Imager at the La Silla Observatory. Using the Astronomical Wide-field Imaging System for Europe environment and the Munich Difference Imaging Analysis pipeline, a module that has been developed for this project, we created the light curves of 16 000 stars with more than 4000 data points which we searched for periodic transit signals using a box-fitting least-squares detection algorithm. All light curves are publicly available. In the course of the pre-OmegaTranS project, we identified two planet candidates - POTS-1b and POTS-C2b - which we present in this work. With extensive follow-up observations we were able to confirm one of them, POTS-1b, a hot Jupiter transiting a mid-K dwarf. The planet has a mass of 2.31 +/- 0.77 M-Jup, a radius of 0.94 +/- 0.04 R-Jup and a period of P = 3.16 d. The host star POTS-1 has a radius of 0.59 +/- 0.02 R-circle dot and a mass of 0.70 +/- 0.05 M-circle dot. Due to its low apparent brightness of I = 16.1 mag, the follow-up and confirmation of POTS-1b was particularly challenging and costly.