Stellar model chromospheres. IV. The formation of the Hepsilon feature in the Sun (G2 V) and Arcturus (K2 III)

The formation of the Balmer series member Hepsilon in the near red wing of the Ca ii H line is discussed for two cases: the Sun (Hepsilon absorption profile) and Arcturus (Hepsilon absorption profile). It is shown that although the Hepsilon source functions in both stars are dominated by the Balmer continuum radiation field through photoionizations, the line formation problems in the two stars are quantitatively different, owing to a substantial difference in the relative importance of the stellar chromosphere temperature inversion compared with the stellar photosphere