Resumo

BOHIGAS, J.. On the evolution of angular momentum, magnetic activity and mass loss rate of late type main sequence stars. Rev. mex. astron. astrofis [online]. 2020, vol.56, n.1, pp.139-171.  Epub 19-Mar-2021. ISSN 0185-1101.  https://doi.org/10.22201/ia.01851101p.2020.56.01.14.

With the best data, I find that nearly all 0.5 to 1.2 M main sequence stars converge to a single rotational mass-dependent sequence after 750 Myr; when M > 0.8 Mʘ , most of them converge in 120 Myr. If stars rotate as rigid bodies, most have angular momenta within clear bounds. The lower bound defines a terminal main sequence rotational isochrone, the upper one coincides with slow rotators from the Pleiades; stars from Praesepe delineate a third one. Mass dependent exponential relationships between angular momentum and age are determined. Age estimates based on the angular momentum are acceptable for stars older than 750 Myr and with M > 0:6 0:7 Mʘ . The Rossby number indicates that the Parker dynamo may cease early on in stars with M/ Mʘ 1.1. An empirical formula and a model for the torque, and a relation between rotational period and magnetic field, lead to a formula for the evolution of the mass loss rate; the present solar rate is near a minimum and was about five times larger when life on Earth started.

Palavras-chave : stars: evolution; stars: late-type; stars: magnetic fields; stars: mass loss; stars: rotation.

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