Understanding the Angular Momentum Loss of Low-Mass Stars: The Case of V374 Peg (1101.1233v1)

Abstract: Recently, surface magnetic field maps had been acquired for a small sample of active M dwarfs, showing that fully convective stars (spectral types ~M4 and later) host intense (~kG), mainly axi-symmetrical poloidal fields. In particular, the rapidly rotating M dwarf V374Peg (M4), believed to lie near the theoretical full convection threshold, presents a stable magnetic topology on a time-scale of 1 yr. The rapid rotation of V374Peg (P=0.44 days) along with its intense magnetic field point toward a magneto-centrifugally acceleration of a coronal wind. In this work, we aim at investigating the structure of the coronal magnetic field in the M dwarf V374Peg by means of three-dimensional magnetohydrodynamical (MHD) numerical simulations of the coronal wind. For the first time, an observationally derived surface magnetic field map is implemented in MHD models of stellar winds for a low-mass star. We self-consistently take into consideration the interaction of the outflowing wind with the magnetic field and vice versa. Hence, from the interplay between magnetic forces and wind forces, we are able to determine the configuration of the magnetic field and the structure of the coronal winds. Our results enable us to evaluate the angular momentum loss of the rapidly rotating M dwarf V374Peg.