IV. The search for Jupiter analogues around solar-like stars
M. Zechmeister1,2, M. Kürster2, M. Endl3, G. Lo Curto4, H. Hartman5,6, H. Nilsson6, T. Henning2, A. P. Hatzes7 and W. D. Cochran3
Institut für Astrophysik, Georg-August-Universität,
2 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
3 McDonald Observatory, University of Texas, Austin, TX 78712, USA
4 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
5 Group for Materials Science and Applied Mathematics, School of Technology, Malmö University, 20506 Malmö, Sweden
6 Lund Observatory, Lund University, PO Box 43, 22100 Lund, Sweden
7 Thüringer Landessternwarte Tautenburg (TLS), Sternwarte 5, 07778 Tautenburg, Germany
Accepted: 13 November 2012
Context. In 1992 we began a precision radial velocity survey for planets around solar-like stars with the Coudé Echelle Spectrograph and the Long Camera (CES LC) at the 1.4 m telescope in La Silla (Chile) resulting in the discovery of the planet ι Hor b. We have continued the survey with the upgraded CES Very Long Camera (VLC) and the HARPS spectrographs, both at the 3.6 m telescope, until 2007.
Aims. In this paper we present additional radial velocities for 31 stars of the original sample with higher precision. The observations cover a time span of up to 15 years and permit a search for Jupiter analogues.
Methods. The survey was carried out with three different instruments/instrument configurations using the iodine absorption cell and the ThAr methods for wavelength calibration. We combine the data sets and perform a joint analysis for variability, trends, and periodicities. We compute Keplerian orbits for companions and detection limits in case of non-detections. Moreover, the HARPS radial velocities are analysed for correlations with activity indicators (CaII H&K and cross-correlation function shape).
Results. We achieve a long-term RV precision of 15 m/s (CES+LC, 1992–1998), 9 m/s (CES+VLC, 1999–2006), and 2.8 m/s (HARPS, 2003–2009, including archive data), respectively. This enables us to confirm the known planetary signals in ι Hor and HR 506 as well as the three known planets around HR 3259. A steady RV trend for ϵ Ind A can be explained by a planetary companion and calls for direct imaging campaigns. On the other hand, we find previously reported trends to be smaller for β Hyi and not present for α Men. The candidate planet ϵ Eri b was not detected despite our better precision. Also the planet announced for HR 4523 cannot be confirmed. Long-term trends in several of our stars are compatible with known stellar companions. We provide a spectroscopic orbital solution for the binary HR 2400 and refined solutions for the planets around HR 506 and ι Hor. For some other stars the variations could be attributed to stellar activity, as e.g. the magnetic cycle in the case of HR 8323.
Conclusions. The occurrence of two Jupiter-mass planets in our sample is in line with the estimate of 10% for the frequency of giant planets with periods smaller than 10 yr around solar-like stars. We have not detected a Jupiter analogue, while the detections limits for circular orbits indicate at 5 AU a sensitivity for minimum mass of at least 1MJup (2MJup) for 13% (61%) of the stars.
Key words: stars: general / planetary systems / techniques: radial velocities / methods: data analysis
Based on observations collected at the European Southern Observatory, La Silla Chile, ESO programmes 50.7-0095, 51.7-0054, 52.7-0002, 53.7-0064, 54.E-0424, 55.E-0361, 56.E-0490, 57.E-0142, 58.E-0134, 59.E-0597, 60.E-0386, 61.E-0589, 62.L-0490, 64.L-0568, 66.C-0482, 67.C-0296, 69.C-0723, 70.C-0047, 71.C-0599, 072.C-0513, 073.C-0784, 074.C-0012, 076.C-0878, 077.C-0530, 078.C-0833, 079.C-0681. Also based on data obtained from the ESO Science Archive Facility.
Appendices are available in electronic form at http://www.aanda.org
Tables of the radial velocities, bisector spans, and are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (22.214.171.124) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/552/A78
© ESO, 2013