Astronomy and Astrophysics, volume 511, A54-54 (2010/2-2)
Do stellar magnetic cycles influence the measurement of precise radial velocities?
SANTOS N.C., GOMES DA SILVA J., LOVIS C. and MELO C.
Abstract (from CDS):
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, Hα, HeI) 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 ∼1m/s.
planetary systems - stars: fundamental parameters - techniques: spectroscopic - techniques: radial velocities - stars: activity - starspots
VizieR on-line data:
<Available at CDS (J/A+A/511/A54): table1.dat table5.dat table6.dat table7.dat table8.dat>
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