Relationship between Ca and Hα chromospheric emission in F-G-K stars: Indication of stellar filaments?

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Table 2

Typical S/N in Ca II and Hα.

S/N	Cat. 1	Cat. 2	Cat. 3	All	Sel. Fig. 10
Ca global	7.3	7.5	12.5	3.7	11.8
Ca LT	7.9	7.8	10.4	4.5	8.0
Ca ST	3.2	2.2	5.11	2.3	4.2
Hα global	2.7	3.0	4.7	3.0	3.7
Hα LT	2.4	3.0	4.2	2.3	3.5
Hα ST	2.1	1.7	2.8	1.9	2.3

Notes. S/N computed for different categories of stars (see Sect. 4.1.1), for the two chromospheric indexes at different timescales. The selection from Fig. 10 (last column) corresponds to the selection of the most variable stars in the middle panel (i.e. LT Ca rms higher than 0.01).

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