Tidal evolution of exoplanetary systems hosting Potentially Habitable Exoplanets. The cases of LHS1140 bc and K218 bc
Abstract
We present a model to study secularly and tidally evolving threebody systems composed by two lowmass planets orbiting a star, in the case where the bodies rotation axes are always perpendicular to the orbital plane. The tidal theory allows us to study the spin and orbit evolution of both stiff Earthlike planets and predominantly gaseous Neptunelike planets. The model is applied to study two recentlydiscovered exoplanetary systems containing potentially habitable exoplanets (PHE): LHS1140 bc and K218 bc. For the former system, we show that both LHS1140 b and c must be in nearlycircular orbits. For K218 bc, the combined analysis of orbital evolution timescales with the current eccentricity estimation of K218 b allows us to conclude that the inner planet (K218 c) must be a Neptunelike gaseous body. Only this would allow for the eccentricity of K218 b to be in the range of values estimated in recent works ($e=0.20 \pm 0.08$), provided that the uniform viscosity coefficient of K218 b is greater than $2.4 \times 10^{19} \ \textrm{Pa s}$ (which is a value characteristic of stiff bodies) and supposing that such system has an age of some Gyr.
 Publication:

arXiv eprints
 Pub Date:
 May 2020
 arXiv:
 arXiv:2005.10318
 Bibcode:
 2020arXiv200510318G
 Keywords:

 Astrophysics  Earth and Planetary Astrophysics
 EPrint:
 9 pages, 6 figures