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Paper: Evolution of chromospheres in red giants
Volume: 9, Cool Stars, Stellar Systems, and the Sun: Sixth Cambridge Workshop
Page: 408
Authors: Dupree, A. K.; Hartmann, L.; Smith, Graeme H.
Abstract: Study of the Mg II chromospheric fluxes in a group of stars with well defined ages reveals that chromospheric activity becomes stronger as low mass stars evolve along the red giant branch. This behavior differs from the evolution of magnetic chromospheres determined for dwarf stars or Population I giant stars, and may represent a chromosphere heated by a different mechanism than magnetic dynamo activity. Stellar pulsation and resulting shock heating represent an attractive alternative heating mechanism, producing a hydrodynamic chromosphere in contrast to the well-known magnetic chromospheres of main sequence stars and warm giants.
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