Hα photometry of IC 4756. a) Standard errors in the STELLA Hα CCD data for both filters (n narrow, w wide). b) Hα index α versus de-reddened b−y color; an activity analog of the H–R diagram. Hα emission increases upward, Hα absorption increases downward. The thick dots indicate the CoRoT stars from Table 1. Spectral type and color equivalents are dF0, ; dK0 ; dM, .
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