摘要：Context.Short- to mid-term magnetic phenomena on the stellar surface of M-type stars can resemble the effects of planets in radial velocity data, and may also hide them.Aims.We analyze 145 spectroscopic HARPS-N observations of GJ 3942 taken over the past five years and additional photometry in order to disentangle stellar activity effects from genuine Doppler signals as a result of the orbital motion of the star around the common barycenter with its planet.Methods.To achieve this, we use the common methods of pre-whitening, and treat the correlated red noise by a first-order moving average term and by Gaussian-process regression following an MCMC analysis.Results.We identify the rotational period of the star at 16.3 days and discover a new super-Earth, GJ 3942 b, with an orbital period of 6.9 days and a minimum mass of 7.1 M⊕. An additional signal in the periodogram of the residuals is present, but at this point we cannot claim with sufficient significance that it is related to a second planet. If confirmed, this planet candidate would have a minimum mass of 6.3 M⊕and a period of 10.4 days, which might indicate a 3:2 mean-motion resonance with the inner planet.
