The HARPS search for southern extra-solar planets - XXIV. Companions to HD 85390, HD 90156, and HD 103197: a Neptune analog and two intermediate-mass planets

We report the detection of three new extrasolar planets orbiting the solar type stars HD 85390, HD 90156 and HD 103197 with the HARPS spectrograph mounted on the ESO 3.6-m telescope at La Silla observatory. HD 85390 has a planetary companion with a projected intermediate mass (42.0 M_⊕) on a 788-day orbit (a = 1.52 AU) with an eccentricity of 0.41, for which there is no analog in the solar system. A drift in the data indicates the presence of another companion on a long-period orbit, which is however not covered by our measurements. HD 90156 is orbited by a warm Neptune analog with a minimum mass of 17.98 M_⊕ (1.05 MM_{neptune}), a period of 49.8 days (a = 0.25 AU), and an eccentricity of 0.31. HD 103197 has an intermediate-mass planet on a circular orbit (P = 47.8 d, M sin i = 31.2 M_⊕). We discuss the formation of planets of intermediate mass ( 30-100 M_⊕), which should be rare inside a few AU according to core accretion formation models.