TY - JOUR
T1 - Planets and stellar activity
T2 - Hide and seek in the CoRoT-7 system
AU - Haywood, R. D.
AU - Collier Cameron, A.
AU - Queloz, D.
AU - Barros, S. C.C.
AU - Deleuil, M.
AU - Fares, R.
AU - Gillon, M.
AU - Lanza, A. F.
AU - Lovis, C.
AU - Moutou, C.
AU - Pepe, F.
AU - Pollacco, D.
AU - Santerne, A.
AU - Ségransan, D.
AU - Unruh, Y. C.
PY - 2014/9
Y1 - 2014/9
N2 - Since the discovery of the transiting super-Earth CoRoT-7b, several investigations have yielded different results for the number and masses of planets present in the system, mainly owing to the star's high level of activity. We re-observed CoRoT-7 in 2012 January with both HARPS and CoRoT, so that we now have the benefit of simultaneous radial-velocity and photometric data. This allows us to use the off-transit variations in the star's light curve to estimate the radialvelocity variations induced by the suppression of convective blueshift and the flux blocked by starspots. To account for activity-related effects in the radial velocities which do not have a photometric signature, we also include an additional activity term in the radial-velocity model, which we treat as a Gaussian process with the same covariance properties (and hence the same frequency structure) as the light curve. Our modelwas incorporated into aMonte Carlo Markov Chain in order to make a precise determination of the orbits of CoRoT-7b and CoRoT-7c. We measure the masses of planets b and c to be 4.73 ± 0.95 and 13.56 ± 1.08M⊕, respectively. The density of CoRoT-7b is (6.61 ± 1.72)(Rp/1.58 R⊕)-3 g cm-3, which is compatible with a rocky composition. We search for evidence of an additional planet d, identified by previous authors with a period close to 9 d. We are not able to confirm the existence of a planet with this orbital period, which is close to the second harmonic of the stellar rotation at ~7.9 d. Using Bayesian model selection, we find that a model with two planets plus activity-induced variations is most favoured.
AB - Since the discovery of the transiting super-Earth CoRoT-7b, several investigations have yielded different results for the number and masses of planets present in the system, mainly owing to the star's high level of activity. We re-observed CoRoT-7 in 2012 January with both HARPS and CoRoT, so that we now have the benefit of simultaneous radial-velocity and photometric data. This allows us to use the off-transit variations in the star's light curve to estimate the radialvelocity variations induced by the suppression of convective blueshift and the flux blocked by starspots. To account for activity-related effects in the radial velocities which do not have a photometric signature, we also include an additional activity term in the radial-velocity model, which we treat as a Gaussian process with the same covariance properties (and hence the same frequency structure) as the light curve. Our modelwas incorporated into aMonte Carlo Markov Chain in order to make a precise determination of the orbits of CoRoT-7b and CoRoT-7c. We measure the masses of planets b and c to be 4.73 ± 0.95 and 13.56 ± 1.08M⊕, respectively. The density of CoRoT-7b is (6.61 ± 1.72)(Rp/1.58 R⊕)-3 g cm-3, which is compatible with a rocky composition. We search for evidence of an additional planet d, identified by previous authors with a period close to 9 d. We are not able to confirm the existence of a planet with this orbital period, which is close to the second harmonic of the stellar rotation at ~7.9 d. Using Bayesian model selection, we find that a model with two planets plus activity-induced variations is most favoured.
KW - Planetary systems
KW - Stars: activity
KW - Stars: individual: CoRot-7
KW - Techniques: radial velocities
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U2 - 10.1093/mnras/stu1320
DO - 10.1093/mnras/stu1320
M3 - Article
AN - SCOPUS:84906070995
SN - 0035-8711
VL - 443
SP - 2517
EP - 2531
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -