  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 188cm 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
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 ~6 R_Earth) around
HAT-P-14 in all bands, a Neptune (~4R_Earth) around HAT-P-11 in all bands, and
a super-Earth (~2.5R_Earth) 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.
