Published in

Astronomy & Astrophysics, (631), p. A90, 2019

DOI: 10.1051/0004-6361/201936267

Links

Tools

Export citation

Search in Google Scholar

Exoplanet characterisation in the longest known resonant chain: the K2-138 system seen by HARPS

Journal article published in 2019 by T. A. Lopez ORCID, S. C. C. Barros ORCID, A. Santerne ORCID, M. Deleuil ORCID, V. Adibekyan ORCID, J.-M. Almenara, D. J. Armstrong ORCID, B. Brugger ORCID, D. Barrado ORCID, D. Bayliss ORCID, I. Boisse, A. S. Bonomo ORCID, F. Bouchy, D. J. A. Brown, E. Carli ORCID and other authors.
This paper was not found in any repository, but could be made available legally by the author.
This paper was not found in any repository, but could be made available legally by the author.

Full text: Unavailable

Green circle
Preprint: archiving allowed
Upload
Green circle
Postprint: archiving allowed
Upload
Green circle
Published version: archiving allowed
Upload
Policy details
Data provided by SHERPA/RoMEO

Abstract

The detection of low-mass transiting exoplanets in multiple systems brings new constraints to planetary formation and evolution processes and challenges the current planet formation theories. Nevertheless, only a mere fraction of the small planets detected by Kepler and K2 have precise mass measurements, which are mandatory to constrain their composition. We aim to characterise the planets that orbit the relatively bright star K2-138. This system is dynamically particular as it presents the longest chain known to date of planets close to the 3:2 resonance. We obtained 215 HARPS spectra from which we derived the radial-velocity variations of K2-138. Via a joint Bayesian analysis of both the K2 photometry and HARPS radial-velocities (RVs), we constrained the parameters of the six planets in orbit. The masses of the four inner planets, from b to e, are 3.1, 6.3, 7.9, and 13.0 M⊕ with a precision of 34, 20, 18, and 15%, respectively. The bulk densities are 4.9, 2.8, 3.2, and 1.8 g cm−3, ranging from Earth to Neptune-like values. For planets f and g, we report upper limits. Finally, we predict transit timing variations of the order two to six minutes from the masses derived. Given its peculiar dynamics, K2-138 is an ideal target for transit timing variation (TTV) measurements from space with the upcoming CHaracterizing ExOPlanet Satellite (CHEOPS) to study this highly-packed system and compare TTV and RV masses.

Beta version