2012A&A...540A.141S

We carried out a radial-velocity survey to search for planets around metal-poor stars. In this paper we report the discovery of two planets around HIP 11952, a metal-poor star with [Fe/H]=-1.9 that belongs to our target sample. Radial velocity variations of HIP 11952 were monitored systematically with FEROS at the 2.2m telescope located at the ESO La Silla observatory from August 2009 until January 2011. We used a cross-correlation technique to measure the stellar radial velocities (RV). We detected a long-period RV variation of 290d and a short-period one of 6.95d. The spectroscopic analysis of the stellar activity reveals a stellar rotation period of 4.8d. The Hipparcos photometry data shows intra-day variabilities, which give evidence for stellar pulsations. Based on our analysis, the observed RV variations are most likely caused by the presence of unseen planetary companions. Assuming a primary mass of 0.83M_☉, we computed minimum planetary masses of 0.78M_Jup for the inner and 2.93M_Jup for the outer planet. The semi-major axes are a₁=0.07AU and a₂=0.81AU, respectively. HIP 11952 is one of very few stars with [Fe/H]←1.0 which have planetary companions. This discovery is important to understand planet formation around metal-poor stars.