Stellar activity noise and planet detection : Alpha Cen B, a laboratory to study activity of solar type stars.

X. Dumusque, F. Pepe, C. Lovis, D. Ségransan, W. Benz, F. Bouchy, M. Mayor, D. Queloz, N. C. Santos, S. Udry

Abstract.
The level of precision achieved by HARPS is opening the way to the discovery of very low-mass and long-period planets. However, activity, characterized by the appearance of magnetic features on the stellar surface, is the main limitation to the radial-velocity (RV) precision. Using RV measurements, we are sensitive to two different noise induced by activity: short-term activity noise that can be seen at rotational periods and long-term activity noise, on timescales similar to the magnetic cycles of solar-type stars. These two different RV perturbations have amplitudes of a few meter-per-seconds on solar-type stars, which is one order of magnitude higher than the signal caused by an Earth-mass habitable planet. Alpha Cen B (HD128621), assumed up to now as the best target to search for an Earth-like habitable planet, has been showing signs of activity in recent years. The HARPS measurements provide an unprecedented data set to study the activity RV effect of solar-type stars. The proposed talk will focus on the characterization of short and long-term activity noise of Alpha Cen B, on the way to correct these noises and finally on the expected planetary detection limits. In conclusion, activity noise will not prevent us of finding Earth-mass habitable planets around quiet solar-type stars.

17th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun
Barcelona, Spain
June 2012

Type: Poster