Volume 511, February 2010
|Number of page(s)||10|
|Section||Planets and planetary systems|
|Published online||09 March 2010|
Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal e-mail: email@example.com
2 Departamento de Matemática Aplicada, Faculdade de Ciências da Universidade do Porto, Portugal
3 Observatoire de Genève, 51 ch. des Maillettes, 1290 Sauverny, Switzerland
4 European Southern Observatory, Casilla 19001, Santiago 19, Chile
Accepted: 14 December 2009
The ever increasing level of precision achieved by present and future radial-velocity instruments is opening the way to discovering very low-mass, long-period planets (e.g. solar-system analogs). These systems will be detectable as low-amplitude signals in radial-velocity (RV). However, an important obstacle to their detection may be the existence of stellar magnetic cycles on similar timescales. Here we present the results of a long-term program to simultaneously measure radial-velocities and stellar-activity indicators (CaII, H, ) for a sample of stars with known activity cycles. Our results suggest that all these stellar activity indexes can be used to trace the stellar magnetic cycle in solar-type stars. Likewise, we find clear indications that different parameters of the HARPS cross-correlation function (BIS, FWHM, and contrast) are also sensitive to activity level variations. Finally, we show that, although in a few cases slight correlations or anti-correlations between radial-velocity and the activity level of the star exist, their origin is still not clear. We can, however, conclude that for our targets (early-K dwarfs) we do not find evidence of any radial-velocity variations induced by variations of the stellar magnetic cycle with amplitudes significantly above ~1 m/s.
Key words: planetary systems / stars: fundamental parameters / techniques: spectroscopic / techniques: radial velocities / stars: activity / starspots
Based on observations collected at the La Silla Parana Observatory, ESO (Chile) with the HARPS spectrograph at the 3.6-m telescope (ESO runs ID 072.C-0096 073.D-0038 074.D-0131 075.D-0194 076.D-0130 078.D-0071 079.D-0075 080.D-0086 081.D-0065)
Tables 5 to 8, with the data used for Figs. 2, 3, and 8, are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (184.108.40.206) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/511/A54
© ESO, 2010
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