A survey of TiO{λ}567 nm absorption in solar-type stars

Molecular absorption bands are estimators of stellar activity and spot cycles on magnetically active stars. We have previously introduced a new color index that compare absorption strength of the titanium oxide (TiO) at 567 nm with nearby continuum. In this paper we implement this index to measure long-term activity variations and the statistical properties of the index in a sample of 302 solar-type stars from the HARPS planet search program. The results indicate a pattern of change in star's activity, covers a range of periods from 2 years up to 17 years.