Photometric follow-up of the transiting planet WASP-1b

We report on photometric follow-up of the recently discovered transiting planet WASP-1b. We observed two transits with the Wise Observatory 1-m telescope, and used a variant of the Eclipsing Binary Orbit Program (EBOP) code together with the Sys-Rem detrending approach to fit the light curve. Assuming a stellar mass of 1.15 M-circle dot, we derived a planetary radius of R-p = 1.40 +/- 0.06R(J) and mass of M-p = 0.87 +/- 0.07M(J). An uncertainty of 15 per cent in the stellar mass results in an additional systematic uncertainty of 5 per cent in the planetary radius and of 10 per cent in planetary mass. Our observations yielded a slightly better ephemeris for the centre of the transit: T-c [HJD] = (245 4013.3127 +/- 0.0004) + N-tr(2.51996 +/- 0.00002). The new planet is an inflated, low-density planet, similar to HAT-P-1b and HD 209458b.