A short-period super-Earth orbiting the M2.5 dwarf GJ3634. Detection with Harps velocimetry and transit search with Spitzer photometry

We report on the detection of GJ3634b, a super-Earth of mass m sin i = 7.0 +/-0.9 Mearth and period P = 2.64561 +/- 0.00066 day. Its host star is a M2.5 dwarf, has a mass of 0.45+/-0.05 Msun, a radius of 0.43+/-0.03 Rsun and lies 19.8+/-0.6 pc away from our Sun. The planet is detected after a radial-velocity campaign using the ESO/Harps spectrograph. GJ3634b had an a priori geometric probability to undergo transit of ~7% and, if telluric in composition, a non-grazing transit would produce a photometric dip of <~0.1%. We therefore followed-up upon the RV detection with photometric observations using the 4.5-micron band of the IRAC imager onboard Spitzer. Our six-hour long light curve excludes that a transit occurs for 2 sigma of the probable transit window, decreasing the probability that GJ3634b undergoes transit to ~0.5%.