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To better understand the observed distributions of rotation rate and magnetic activity of sun-like and low-mass stars, we derive a physically motivated scaling for the dependence of the stellar-wind torque on Rossby number. The torque also contains an empirically-derived scaling with stellar mass (and radius), which provides new insight into the mass-dependence of stellar magnetic and wind properties. We demonstrate that this new formulation explains why the lowest mass stars are observed to maintain rapid rotation for much longer than solar-mass stars, and simultaneously, why older populations exhibit a sequence of slowly rotating stars, in which the low-mass stars rotate more slowly than solar-mass stars. The model also reproduces some previously unexplained features in the period-mass diagram for the Kepler field, notably: the particular shape of the upper envelope of the distribution, suggesting that ~95% of Kepler field stars with measured rotation periods are younger than ~4 Gyr; and the shape of the lower envelope, corresponding to the location where stars transition between magnetically saturated and unsaturated regimes.
Asteroseismology of 1.0-2.0 Msun red giants by the Kepler satellite has enabled the first definitive measurements of interior rotation in both first ascent red giant branch (RGB) stars and those on the Helium burning clump. The inferred rotation rate
Context. Monitoring of the photometric and chromospheric HK emission data series of stars similar to the Sun in age and average activity level showed that there is an empirical correlation between the average stellar chromospheric activity level and
We present a summary of the splinter session Sun-like stars unlike the Sun that was held on 09 June 2016 as part of the Cool Stars 19 conference (Uppsala, Sweden). We discussed the main limitations (in the theory and observations) in the derivation o
Magnetic fields play an important role at all stages of stellar evolution. In Sun-like stars, they are generated in the outer convective layers. Studying the large-scale magnetic fields of these stars enlightens our understanding of the field propert
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 r