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2018ApJ...863..166V - Astrophys. J., 863, 166-166 (2018/August-3)

Chemo-kinematic ages of eccentric-planet-hosting M dwarf stars.


Abstract (from CDS):

The M dwarf stars are exciting targets for exoplanet investigations; however, their fundamental stellar properties are difficult to measure. Perhaps the most challenging property is stellar age. Once on the main sequence, M dwarfs change imperceptibly in their temperature and luminosity, necessitating novel statistical techniques for estimating their ages. In this paper, we infer ages for known eccentric-planet-hosting M dwarfs using a combination of kinematics and α-element enrichment, both shown to correlate with age for Sun-like FGK stars. We calibrate our method on FGK stars in a Bayesian context. To measure α-enrichment, we use publicly available spectra from the CARMENES exoplanet survey and a recently developed [Ti/Fe] calibration utilizing individual Ti I and Fe I absorption lines in the Y band. Tidal effects are expected to circularize the orbits of short-period planets on short timescales; however, we find a number of mildly eccentric, close-in planets orbiting old (∼8 Gyr) stars. For these systems, we use our ages to constrain the tidal dissipation parameter of the planets, Qp. For two mini-Neptune planets, GJ 176 b and GJ 536 b, we find that they have Qp values more similar to the ice giants than to the terrestrial planets in our solar system. For GJ 436 b, we estimate an age of 8.9–2.1+2.3Gyr and constrain the Qp to be >105, in good agreement with constraints from its inferred tidal heating. We find that GJ 876 d has likely undergone significant orbital evolution over its 8.4–2.0+2.2Gyr lifetime, potentially influenced by its three outer companions that orbit in a Laplace resonance.

Abstract Copyright: © 2018. The American Astronomical Society. All rights reserved.

Journal keyword(s): planets and satellites: dynamical evolution and stability - planets and satellites: gaseous planets - stars: abundances - stars: fundamental parameters - stars: late-type - stars: low-mass

Simbad objects: 35

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