SuperWASP observations of the transiting extrasolar planet XO-1b

We report on observations of 11 transit events of the transiting extrasolar planet XO-1b by the SuperWASP North observatory. From our data, obtained during 2004 May-September, we find that the XO-1b orbital period is 3.941634 +/- 0.000137 days, the planetary radius is 1.34RJ +/- 0.12RJ, and the inclination is 88.92d +/- 1.04d, in good agreement with previously published values. We tabulate the transit timings from 2004 SuperWASP and XO data, which are the earliest obtained for XO-1b and which will therefore be useful for future investigations of timing variations caused by additional perturbing planets. We also present an ephemeris for the transits.