The HARPS search for southern extra-solar planets XXI. Three new giant planets orbiting the metal-poor stars HD 5388, HD 181720, and HD 190984

We present the discovery of three new giant planets around three metal-deficient stars: HD5388 b (1.96 M(Jup)), HD 181720 b (0.37 M(Jup)), and HD190984 b (3.1 M(Jup)). All the planets have moderately eccentric orbits (ranging from 0.26 to 0.57) and long orbital periods (from 777 to 4885 days). Two of the stars (HD181720 and HD190984) were part of a program searching for giant planets around a sample of similar to 100 moderately metal-poor stars, while HD5388 was part of the volume-limited sample of the HARPS GTO program. Our discoveries suggest that giant planets in long period orbits are not uncommon around moderately metal-poor stars.