Volume 631, November 2019
|Number of page(s)||12|
|Section||Planets and planetary systems|
|Published online||15 October 2019|
Nearly polar orbit of the sub-Neptune HD 3167 c
Constraints on the dynamical history of a multi-planet system
Institut d’astrophysique de Paris (IAP), UMR 7095 CNRS, Université Pierre & Marie Curie,
98bis Boulevard Arago,
2 Observatoire de Haute-Provence (OHP), CNRS, Université d’Aix-Marseille, 04870 Saint-Michel-l’Observatoire, France
3 IMCCE, CNRS-UMR 8028, Observatoire de Paris, PSL University, Sorbonne Université, 77 avenue Denfert-Rochereau, 75014 Paris, France
4 Observatoire de l’Université de Geneve, 51 chemin des Maillettes, Versoix, Switzerland
5 CFisUC, Department of Physics, University of Coimbra, 3004-516 Coimbra, Portugal
Accepted: 26 June 2019
Aims. We present the obliquity measurement, that is, the angle between the normal angle of the orbital plane and the stellar spin axis, of the sub-Neptune planet HD 3167 c, which transits a bright nearby K0 star. We study the orbital architecture of this multi-planet system to understand its dynamical history. We also place constraints on the obliquity of planet d based on the geometry of the planetary system and the dynamical study of the system.
Methods. New observations obtained with HARPS-N at the Telescopio Nazionale Galileo (TNG) were employed for our analysis. The sky-projected obliquity was measured using three different methods: the Rossiter-McLaughlin anomaly, Doppler tomography, and reloaded Rossiter-McLaughlin techniques. We performed the stability analysis of the system and investigated the dynamical interactions between the planets and the star.
Results. HD 3167 c is found to be nearly polar with sky-projected obliquity, λ = −97°± 23°. This misalignment of the orbit of planet c with the spin axis of the host star is detected with 97% confidence. The analysis of the dynamics of this system yields coplanar orbits of planets c and d. It also shows that it is unlikely that the currently observed system can generate this high obliquity for planets c and d by itself. However, the polar orbits of planets c and d could be explained by the presence of an outer companion in the system. Follow-up observations of the system are required to confirm such a long-period companion.
Key words: techniques: radial velocities / planets and satellites: fundamental parameters / planet–star interactions / planets and satellites: individual: HD 3167
© S. Dalal et al. 2019
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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