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Keywords:

  • planetary systems;
  • stars: activity;
  • starspots;
  • Sun: activity;
  • techniques: radial velocities

Abstract

Stellar activity induced by spots and plages, even at a low level of activity, affects the radial velocity signatures. It is therefore crucial to determine how it impacts our ability to detect small planetary signals such as those produced by Earth-mass planets in the habitable zone of stars. We focus on the solar case: thanks to the wealth of accurate data available, the Sun gives us a unique opportunity to test the impact of stellar activity on such detections. We use the Sun as a template and investigate in details the impact of spots and plages as well as the role played by the attenuation of convection due to the presence of magnetic activity. We present the detection limits obtained in various conditions. We find that the plage contribution due to the convective blueshift attenuation dominates the total signal, with a peak-to-peak amplitude over the solar cycle of about 8 m s–1, and show that this contribution would prevent the detection of the Earth around the Sun, even with forthcoming high precision radial velocity instruments, unless ways to correct the signal are found. We therefore propose practical ways to correct for the activity on various timescales from days to years, and use again the Sun to estimate the ultimate detection limits achievable once the signal is corrected from the Sun's activity. Estimations will be briefly presented. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)