Motalebi, F.Udry, S.Gillon, M.Lovis, C.Ségransan, D.Buchhave, L. A.Demory, B. O.Malavolta, L.Dressing, Courtney DanielleSasselov, DimitarRice, K.Charbonneau, DavidCollier Cameron, A.Latham, DavidMolinari, E.Pepe, F.Affer, L.Bonomo, A. S.Cosentino, R.Dumusque, X.Figueira, P.Fiorenzano, A. F. M.Gettel, S.Harutyunyan, A.Haywood, RaphaelleJohnson, JohnLopez, E.Lopez-Morales, MariaMayor, M.Micela, G.Mortier, A.Nascimbeni, V.Philips, D.Piotto, G.Pollacco, D.Queloz, D.Sozzetti, A.Vanderburg, A.Watson, C. A.2017-03-152015Motalebi, F., S. Udry, M. Gillon, C. Lovis, D. Ségransan, L. A. Buchhave, B. O. Demory, et al. 2015. “The HARPS-N Rocky Planet Search.” A&A 584 (November 24): A72. doi:10.1051/0004-6361/201526822.0004-6361http://nrs.harvard.edu/urn-3:HUL.InstRepos:30781103We know now from radial velocity surveys and transit space missions that planets only a few times more massive than our Earth are frequent around solar-type stars. Fundamental questions about their formation history, physical properties, internal structure, and atmosphere composition are, however, still to be solved. We present here the detection of a system of four low-mass planets around the bright (V = 5.5) and close-by (6.5 pc) star HD 219134. This is the first result of the Rocky Planet Search programme with HARPS-N on the Telescopio Nazionale Galileo in La Palma. The inner planet orbits the star in 3.0935 ± 0.0003 days, on a quasicircular orbit with a semi-major axis of 0.0382 ± 0.0003 AU. Spitzer observations allowed us to detect the transit of the planet in front of the star making HD 219134 b the nearest known transiting planet to date. From the amplitude of the radial velocity variation (2.25 ± 0.22 ms−1 ) and observed depth of the transit (359 ± 38 ppm), the planet mass and radius are estimated to be 4.36 ± 0.44 M⊕ and 1.606 ± 0.086 R⊕, leading to a mean density of 5.76 ± 1.09 g cm−3 , suggesting a rocky composition. One additional planet with minimum-mass of 2.78 ± 0.65 M⊕ moves on a close-in, quasi-circular orbit with a period of 6.767 ± 0.004 days. The third planet in the system has a period of 46.66 ± 0.08 days and a minimum-mass of 8.94 ± 1.13 M⊕, at 0.233 ± 0.002 AU from the star. Its eccentricity is 0.46 ± 0.11. The period of this planet is close to the rotational period of the star estimated from variations of activity indicators (42.3 ± 0.1 days). The planetary origin of the signal is, however, the preferred solution as no indication of variation at the corresponding frequency is observed for activity-sensitive parameters. Finally, a fourth additional longer-period planet of mass of 71 M⊕ orbits the star in 1842 days, on an eccentric orbit (e = 0.34 ± 0.17) at a distance of 2.56 AU.en-UStechniques: radial velocitiestechniques: photometricstars: individual: HD 219134binaries: eclipsinginstrumentation: spectrographsJournal Article2017-03-1510.1051/0004-6361/201526822