Journal
ASTRONOMY & ASTROPHYSICS
Volume 511, Issue -, Pages -Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361/200913433
Keywords
planetary systems; stars: fundamental parameters; techniques: spectroscopic; techniques: radial velocities; stars: activity; starspots
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Funding
- Fundacao para a Ciencia e a Tecnologia (FCT), Portugal [PTDC/CTEAST/098528/2008, PTDC/CTE-AST/098604/2008]
- EC
- FCT [POCI2010]
- FEDER
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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-alpha, He I) 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 similar to 1 m/s.
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