Detection of a transit of the super-Earth 55 Cnc e with Warm Spitzer

astro-ph.EP

/ Authors

B. -O. Demory, M. Gillon, D. Deming, D. Valencia, S. Seager, B. Benneke, C. Lovis, P. Cubillos, J. Harrington, K. B. Stevenson

and 5 more authors

M. Mayor, F. Pepe, D. Queloz, D. Segransan, S. Udry

/ Abstract

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 410 +- 63 ppm, which translates to a planetary radius of 2.08 +- 0.16 R_Earth as measured in IRAC 4.5-micron channel. A planetary mass of 7.81 +- 0.58 M_Earth is derived from an extensive set of radial-velocity data, yielding a mean planetary density of 4.8 +- 1.3 g cm-3. 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.