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Planets and stellar activity : hide and seek in the CoRoT-7 system
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Haywood, R. D., Collier Cameron, A., Queloz, D., Barros, S. C. C., Deleuil, M., Fares, R., Gillon, M., Lanza, A. F., Lovis, C., Moutou, C., Pepe, F., Pollacco, Don, Santerne, A., Segransan, D. and Unruh, Y. C. (2014) Planets and stellar activity : hide and seek in the CoRoT-7 system. Monthly Notices of the Royal Astronomical Society, Volume 443 (Number 3). pp. 2517-2531. doi:10.1093/mnras/stu1320 ISSN 0035-8711.
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Official URL: http://dx.doi.org/10.1093/mnras/stu1320
Abstract
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 radial-velocity 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 model was incorporated into a Monte 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 ± 1.08 M⊕, 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.
Item Type: | Journal Article | ||||||||||
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||||
Journal or Publication Title: | Monthly Notices of the Royal Astronomical Society | ||||||||||
Publisher: | Oxford University Press | ||||||||||
ISSN: | 0035-8711 | ||||||||||
Official Date: | 21 September 2014 | ||||||||||
Dates: |
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Volume: | Volume 443 | ||||||||||
Number: | Number 3 | ||||||||||
Page Range: | pp. 2517-2531 | ||||||||||
DOI: | 10.1093/mnras/stu1320 | ||||||||||
Status: | Peer Reviewed | ||||||||||
Publication Status: | Published | ||||||||||
Access rights to Published version: | Restricted or Subscription Access | ||||||||||
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