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

TL;DR

This study reports the discovery of a super-Earth orbiting an M2.5 dwarf star, combining radial velocity measurements from HARPS with transit search observations from Spitzer, and concludes that the planet likely does not transit its host star.

Contribution

First detection of a super-Earth around an M dwarf using combined HARPS radial velocities and Spitzer photometry, demonstrating an effective method for characterizing such planets.

Findings

Super-Earth GJ3634b has a mass of 7.0 +/- 0.9 Mearth and a 2.64561-day orbit.

Spitzer photometry rules out transits with 2 sigma confidence.

Transit probability is reduced to approximately 0.5% after observations.

Abstract

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%.