  Capella is a spectroscopic binary consisting of two G-type giants, where the
primary (G8III) is a normal red-clump giant while the secondary (G0III) is a
chromospherically-active fast rotator showing considerable overabundance of Li
as Li-enhanced giants. Recently, Takeda & Tajitsu (2017) reported that
abundance ratios of specific light elements (e.g., [C/Fe] or [O/Fe]) in Li-rich
giants of high activity tend to be anomalously high, which they suspected to be
nothing but superficial caused by unusual atmospheric structure due to high
activity. Towards verifying this hypothesis, we determined the elemental
abundances of the primary and the secondary of Capella based on the
disentangled spectrum of each component, in order to see whether any apparent
disagreement exists between the two, which should have been formed with the
same chemical composition. We found that the primary is slightly supersolar (by
~+0.1dex) while the secondary is subsolar (by several tenths dex) for heavier
elements such as Fe, resulting in a marked discrepancy between the primary and
secondary, though such a trend is not seen for light elements (e.g., C or O).
These observational facts suggest that anomalously large [X/Fe] ratios found in
Li-rich giants were mainly due to an apparent decrease of Fe abundance, which
we speculate is caused by the overionization effect due to chromospheric UV
radiation. We thus conclude that conventional model atmosphere analysis would
fail to correctly determine the abundances of fast-rotating giants of high
activity, for which proper treatment of chromospheric effect is required for
deriving true photospheric abundances.
