DEMONSTRATING HIGH-PRECISION, MULTIBAND TRANSIT PHOTOMETRY WITH MUSCAT: A CASE FOR HAT-P-14B

The Multicolor Simultaneous Camera for studying Atmospheres of Transiting exoplanets (MuSCAT) is an optical three-band (g(2)'-, r(2)'- and z(s,2) -band) imager that was recently developed for the 188 cm telescope at Okayama Astrophysical Observatory with the aim of validating and characterizing transiting planets. In a pilot observation with MuSCAT we observed a primary transit of HAT-P-14b, a high-surface gravity (g(p) = 38 ms(-2)) hot Jupiter around a bright (V = 10) F-type star. From a 2.9 hr observation we achieved the five-minute binned photometric precisions of 0.028%, 0.022%, and 0.024% in the g(2)', r(2)', and z(s,2) bands, respectively, which provided the highest quality photometric data for this planet. Combining these results with those of previous observations, we search for variations of transit timing and duration over five years as well as variations of planet-star radius ratio (R-p/R-s) with wavelengths, but can find no considerable variation in any parameters. On the other hand, using the transit subtracted light curves we simulate the achievable measurement error of R-p/R-s with MuSCAT for various planetary sizes, assuming three types of host stars: HAT-P-14, the nearby K-dwarf HAT-P-11, and the nearby M-dwarf GJ1214. Comparing our results with the expected atmospheric scale heights, we find that MuSCAT is capable of probing the atmospheres of planets as small as a sub-Jupiter (R-p similar to 6R(circle plus)) around HAT-P-14 in all bands, a Neptune (similar to 4R(circle plus)) around HAT-P-11 in all bands, and a super-Earth (similar to 2.5R(circle plus)) around GJ1214 in r(2)' and z(s,2) bands. These results promise that MuSCAT will produce fruitful scientific outcomes in the K2 and TESS era.