Magneto-convective models of red dwarfs: constraints imposed by the lithium abundance

Abstract

Magnetic fields impede the onset of convection, thereby altering the thermal structure of a convective envelope in a low mass star: this has an effect on the amount of lithium depletion in a magnetized star. In order to quantify this effect, we have applied a magneto-convective model to two low mass stars for which lithium abundances and precise structural parameters are known: YY Gem and CU Cnc. For both stars, we have obtained models which satisfy empirical constraints on the following parameters: R, L, surface magnetic field strength, and Li abundance. In the case of YY Gem, we have obtained a model which satisfies the empirical constraints with an internal magnetic field of several megagauss: such a field strength is within the range of a dynamo where the field energy is in equipartition with rotational energy deep inside the convection zone. However, in the case of CU Cnc, the Li requires an internal magnetic field which is probably too strong for a dynamo origin: we suggest possible alternatives which might account for the reported Li abundance in CU Cnc.

arXiv commentAccepted for publication by MNRAS

References in corpus (12)

• Absolute dimensions of the M-type eclipsing binary YY Geminorum (Castor C): a challenge to evolutionary models in the lower main-sequence
• Large-scale magnetic topologies of late M dwarfs
• Simulations of dynamo action in fully convective stars
• 10,000 Standard Solar Models: a Monte Carlo Simulation
• Solar System Abundances of the Elements
• Stellar Models with Microscopic Diffusion and Rotational Mixing I: Application to the Sun
• Magnetic Inhibition of Convection and the Fundamental Properties of Low-Mass Stars. I. Stars with a Radiative Core
• Fundamental properties of lower main-sequence stars
• A Tale of Two Anomalies: Depletion, Dispersion, and the Connection Between the Stellar Lithium Spread and Inflated Radii on the Pre-Main Sequence
• Magneto-Convection and Lithium Age Estimates of the βPictoris Moving Group
• The effect of starspots on the ages of low-mass stars determined from the lithium depletion boundary
• Solar-cycle variation of sound speed near the solar surface

Cited by in corpus (4)

• Magnetic Inhibition of Convection and the Fundamental Properties of Low-Mass Stars. III. A Consistent 10 Myr Age for the Upper Scorpius OB Association
• Magnetic modeling of inflated low-mass stars using interior fields no larger than ~10 kilogauss
• Theoretical limits on magnetic field strengths in low-mass stars
• The Radius and Entropy of a Magnetized, Rotating Fully-convective Star: Analysis With Depth-dependent Mixing Length Theories