The Transit Light Curve Project. I. Four Consecutive Transits of the Exoplanet XO-1b
We present RIz photometry of four consecutive transits of the newly discovered exoplanet XO-1b. We improve on the estimates of the transit parameters, finding the planetary radius to be RP = 1.184 +0.028 -0.018 RJ, and the stellar radius to be R* = 0.928 +0.018 -0.013 R☉, assuming a stellar mass of M* = (1.00 ± 0.03) M☉. The uncertainties in the planetary and stellar radii are dominated by the uncertainty in the stellar mass. These uncertainties increase by a factor of 2-3 if a more conservative uncertainty of 0.10 M☉ is assumed for the stellar mass. Our estimate of the planetary radius is smaller than that reported by McCullough and coworkers, and the resulting estimate for the mean density of XO-1b is intermediate between that of the low-density planet HD 209458b and the higher density planets TrES-1 and HD 189733b. The timings of the transits have an accuracy ranging from 0.2 to 2.5 minutes and are marginally consistent with a uniform period.
Additional Information© 2006. The American Astronomical Society. Received 2006 June 19; accepted 2006 July 26. Print publication: Issue 2 (2006 December 1). We thank T. Spahr for swapping telescope nights on short notice, E. Falco for accommodating our observing schedule changes, S. Gaudi for lengthy discussions about the MCMC method and numerous suggestions for improving the manuscript, J. Fernández for helpful discussions about fitting transit light curves, G. Torres for help with stellar isochrones, and R. Kurucz for calculations of limb-darkening coefficients. We thank A. Soderberg, S. B. Cenko, and E. O. Ofek for their help in obtaining the Palomar 1.5 m photometry. We also thank the anonymous referee for an exceptionally careful review of the manuscript. KeplerCam was developed with partial support from the Kepler mission under NASA Cooperative Agreement NCC2-1390 (PI: D. Latham), and the KeplerCam observations described in this paper were partly supported by grants from the Kepler mission to SAO and PSI. The TopHAT observations were supported by NASA grant NNG04GN74G. Work by G.B. was supported by NASA through grant HST-HF-01170.01-A, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. Work by F.T.O'D and D.C. was supported by NASA under grant NNG05GJ29G, issued through the Origins of Solar Systems Program.
Published - HOLapj06.pdf