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Convective motions at the stellar surface generate a stochastic colored noisesource in the radial velocity (RV) data. This noise impedes the detection ofsmall exoplanets. Moreover, the unknown statistics (amplitude, distribution)related to this noise make it difficult to estimate the false alarm probability(FAP) for exoplanet detection tests. In this paper, we investigate thepossibility of using 3D magneto-hydrodynamical simulations (MHD) of stellarconvection to design detection methods that can provide both a reliableestimate of the FAP and a high detection power. We tested the realism of 3Dsimulations in producing solar RV by comparing them with the observed diskintegrated velocities taken by the GOLF instrument on board the SOHOspacecraft. We presented a new detection method based on periodogramsstandardized by these simulated time series, applying several detection teststo these standarized periodograms. The power spectral density of the 3Dsynthetic convective noise is consistent with solar RV observations for shortperiods. For regularly sampled observations, the analytic expressions of FAPderived for several statistical tests applied to the periodogram standardizedby 3D simulation noise are accurate. The adaptive tests considered in this work(Higher-Criticism, Berk-Jones), which are new in the exoplanet field, may offerbetter detection performance than classical tests (based on the highestperiodogram value) in the case of multi-planetary systems and planets witheccentric orbits. 3D MHD simulations are now mature enough to produce reliablesynthetic time series of the convective noise affecting RV data. These seriescan be used to access to the statistics of this noise and derive accurate FAPof tests that are a critical element in the detection of exoplanets down to thecm/s level.

astronomy and astrophysics

3D magneto-hydrodynamical simulations of stellar convective noise for  improved exoplanet detection. I. Case of regularly sampled radial velocity  observations