Volume 633, January 2020
|Number of page(s)||6|
|Section||Planets and planetary systems|
|Published online||09 January 2020|
Circumstellar environment of 55 Cancri
The super-Earth 55 Cnc e as a primary target for star–planet interactions★
IRAP, Université de Toulouse, CNRS, UPS, CNES,
2 Trinity College Dublin, College Green, Dublin 2, Ireland
3 Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
4 Department of Physics and Kavli Institute for Astrophysics and Space Research, MIT, Cambridge, MA 02139, USA
Accepted: 8 December 2019
Context. 55 Cancri hosts five known exoplanets, most notably the hot super-Earth 55 Cnc e, which is one of the hottest known transiting super-Earths.
Aims. Because of the short orbital separation and host star brightness, 55 Cnc e provides one of the best opportunities for studying star-planet interactions (SPIs). We aim to understand possible SPIs in this system, which requires a detailed understanding of the stellar magnetic field and wind impinging on the planet.
Methods. Using spectropolarimetric observations and Zeeman Doppler Imaging, we derived a map of the large-scale stellar magnetic field. We then simulated the stellar wind starting from the magnetic field map, using a 3D magneto-hydrodynamic model.
Results. The map of the large-scale stellar magnetic field we derive has an average strength of 3.4 G. The field has a mostly dipolar geometry; the dipole is tilted by 90° with respect to the rotation axis and the dipolar strength is 5.8 G at the magnetic pole. The wind simulations based on this magnetic geometry lead us to conclude that 55 Cnc e orbits inside the Alfvén surface of the stellar wind, implying that effects from the planet on the wind can propagate back to the stellar surface and result in SPI.
Key words: stars: individual: 55 Cnc / stars: magnetic field / stars: late-type / stars: winds, outflows / planetary systems / planet–star interactions
© ESO 2020
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