2012A&A...546A..27B

We report on the discovery of GJ 3470b, a transiting hot Uranus of mass m_p=14.0±1.8M_⊕, radius R_p=4.2±0.6R_⊕ and period P=3.3371±0.0002day. Its host star is a nearby (d=25.2±2.9pc) M1.5 dwarf of mass M_*=0.54±0.07M_☉ and radius R_*=0.50±0.06R_☉. The detection was made during a radial-velocity campaign with Harps that focused on the search for short-period planets orbiting M dwarfs. Once the planet was discovered and the transit-search window narrowed to about 10% of an orbital period, a photometric search started with Trappist and quickly detected the ingress of the planet. Additional observations with Trappist, EulerCam and Nites definitely confirmed the transiting nature of GJ3470b and allowed the determination of its true mass and radius. The star's visible or infrared brightness (V^mag=12.3, K^mag=8.0), together with a large eclipse depth D=0.57±0.05%, ranks GJ3470b among the most suitable planets for follow-up characterizations.