Planetary companions around the metal-poor star HIP 11952
1 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
2 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
3 Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
4 Astronomisches Rechen-Institut, Zentrum für Astronomie, Mönchhofstrasse, 12-14, 69120 Heidelberg, Germany
5 Institut für Astrophysik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
6 European Southern Observatory, Karl-Schwarzschild Str. 2, 85748 Garching bei München, Germany
7 University of Würzburg, Department of Radiation Oncology, 97080 Würzburg, Germany
Received: 4 August 2011
Accepted: 27 February 2012
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.
Key words: stars: abundances / techniques: spectroscopic / planetary systems / techniques: radial velocities / stars: individual: HIP 11952
© ESO, 2012