Detection of a transit of the super-Earth 55 Cnc e with Warm Spitzer
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We report on the detection of a transit of the super-Earth 55 Cnc e with Warm Spitzer in IRAC’s 4.5-micron band. Our MCMC analysis includes an extensive modeling of the systematic effects affecting Warm Spitzer photometry, and yields a transit depth of 450 +- 50 ppm, which translates to a planetary radius of 2.13 +- 0.14 Earth Radii as measured in IRAC 4.5-micron channel. A planetary mass of 7.98 +- 0.69 Earth Masses is derived from an extensive set of radial-velocity data, yielding a planetary density of 0.83 +- 0.18 Earth density. Interestingly, the derived radius is 1.3 times larger than the one recently reported in the visible by Winn et al. Thanks to the brightness of its host star (V=6, K=4), 55 Cnc e is a unique target for the thorough characterization of a super-Earth orbiting around a solar-type star.
