<BR /> Aims: 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. <BR /> Methods: Radial velocity variations of HIP 11952 were monitored systematically with FEROS at the 2.2 m 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). <BR /> Results: We detected a long-period RV variation of 290 d and a short-period one of 6.95 d. The spectroscopic analysis of the stellar activity reveals a stellar rotation period of 4.8 d. 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 0.83 M<SUB>☉</SUB>, we computed minimum planetary masses of 0.78 M<SUB>Jup</SUB> for the inner and 2.93 M<SUB>Jup</SUB> for the outer planet. The semi-major axes are a<SUB>1</SUB> = 0.07 AU and a<SUB>2</SUB> = 0.81 AU, respectively. <BR /> Conclusions: 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.
Planetary companions around the metal-poor star HIP 11952
Roccatagliata, V.Co-primo
;
2012-01-01
Abstract
Aims: 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.
Methods: Radial velocity variations of HIP 11952 were monitored systematically with FEROS at the 2.2 m 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).
Results: We detected a long-period RV variation of 290 d and a short-period one of 6.95 d. The spectroscopic analysis of the stellar activity reveals a stellar rotation period of 4.8 d. 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 0.83 M☉, we computed minimum planetary masses of 0.78 MJup for the inner and 2.93 MJup for the outer planet. The semi-major axes are a1 = 0.07 AU and a2 = 0.81 AU, respectively.
Conclusions: 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.
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