Abstract
We have measured the He I D3 line λ5876 Å, in 32 F-type young open cluster stars and in 4 field stars. Combining our results with previous observations of D3 we strengthen the following conclusions: (a) Sub-surface convective zones appear, on the main sequence, around F0 (B - V ∼ 0.3). (b) The stars between F0 nd F5 (0.3 ≾ B - V ≲ 0.42) are chromospherically “active” irrespective of age, which implies a heating mechanism not affected by evolutionary effects. In this range the activity in D3 and X-rays are uncorrelated. (c) For stars later than F5 the correlation among all the activity indices, chromospheric and coronal, shows a common energy source. Convective zones here should be deep enough to generate magnetic fields capable of supplying this energy, and also for braking the rotation.
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García López, R.J., Rebolo, R., Beckman, J.E., McKeith, C.D. (1991). He I 5876 å line in the study of chromospheric activity in F-type MS stars. In: Tuominen, I., Moss, D., Rüdiger, G. (eds) The Sun and Cool Stars: activity, magnetism, dynamos. Lecture Notes in Physics, vol 380. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-53955-7_183
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DOI: https://doi.org/10.1007/3-540-53955-7_183
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