Ca II H high-resolution spectral monitoring of active late-type dwarfs
Abstract
We have monitored Ca II H with a spectral resolution of 8 x 104, in a sample of late-type MS stars over a four-year period. The high resolution enables us to add information on velocity fields to the usual flux monitoring. We detect changes in wavelength of different parts of the Ca II H feature, which can be interpreted as velocity fields in the lower chromosphere, with downflow and upflow of order 0.5 km s-1, depending on the star. Flux variations in Ca II H emission can be ascribed, via velocity tagging, to long-term change in plage cover rather than short-term modulation by (incompletely sampled) rotation cycles.
- Publication:
-
IAU Colloq. 130: The Sun and Cool Stars. Activity, Magnetism, Dynamos
- Pub Date:
- 1991
- DOI:
- 10.1007/3-540-53955-7_180
- Bibcode:
- 1991LNP...380..463B