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arXiv · 1709.06851

HADES RV Programme with HARPS-N at TNG VI. GJ 3942 b behind dominant activity signals

M. Perger·I. Ribas·M. Damasso·J. C. Morales·L. Affer·A. Suárez Mascareño·G. Micela·J. Maldonado·J. I. González Hernández·R. Rebolo·G. Scandariato·G. Leto·R. Zanmar Sanchez·S. Benatti·A. Bignamini·F. Borsa·A. Carbognani·R. Claudi·S. Desidera·M. Esposito·M. Lafarga·A. F. Martinez Fiorenzano·E. Herrero·E. Molinari·V. Nascimbeni·I. Pagano·M. Pedani·E. Poretti·M. Rainer·A. Rosich·A. Sozzetti·B. Toledo-Padrón
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Abstract

Short- to mid-term magnetic phenomena on the stellar surface of M-type stars cannot only resemble the effects of planets in radial velocity data, but also may hide them. We analyze 145 spectroscopic HARPS-N observations of GJ 3942 taken over the past five years and additional photometry 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. 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. 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 Me. An additional signal in the periodogram of the residuals is present but we cannot claim it to be related to a second planet with sufficient significance at this point. If confirmed, such planet candidate would have a minimum mass of 6.3 Me and a period of 10.4 days, which might indicate a 3:2 mean-motion resonance with the inner planet.

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M. Perger, I. Ribas, M. Damasso, J. C. Morales, L. Affer, A. Suárez Mascareño, G. Micela, J. Maldonado, J. I. González Hernández, R. Rebolo, G. Scandariato, G. Leto, R. Zanmar Sanchez, S. Benatti, A. Bignamini, F. Borsa, A. Carbognani, R. Claudi, S. Desidera, M. Esposito, M. Lafarga, A. F. Martinez Fiorenzano, E. Herrero, E. Molinari, V. Nascimbeni, I. Pagano, M. Pedani, E. Poretti, M. Rainer, A. Rosich, A. Sozzetti, B. Toledo-Padrón. 2017-09-20. HADES RV Programme with HARPS-N at TNG VI. GJ 3942 b behind dominant activity signals. https://doi.org/10.1051/0004-6361%2F201731307

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