On the evolution of angular momentum, magnetic activity and mass loss rate of late type main sequence stars
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 de...
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| Format: | article |
| Status: | Published version |
| Publication Date: | 2020 |
| Country: | México |
| Institution: | Universidad Nacional Autónoma de México |
| Repository: | Redalyc-UNAM |
| OAI Identifier: | oai:redalyc.org:57171642014 |
| Online Access: | https://www.redalyc.org/articulo.oa?id=57171642014 https://www.redalyc.org/journal/571/57171642014/ https://www.redalyc.org/journal/571/57171642014/html/ https://www.redalyc.org/journal/571/57171642014/57171642014.epub https://www.redalyc.org/journal/571/57171642014/movil |
| Access Level: | Open access |
| Keyword: | Física, Astronomía y Matemáticas type stars: late stars: rotation Stars: evolution stars: mass loss |
| Summary: | 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. |
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