  We have derived CNO abundances in 12 RR Lyrae stars. Four stars show [C/Fe]
near 0.0 and two stars show [C/Fe] = 0.52 and 0.65. Red giant branch stars,
which are known to be the predecessors of RR Lyrae stars, generally show a
deficiency of carbon due to proton captures during their evolution from the
main sequence up the giant branch. We suggest that the enhancement of carbon is
due to production during the helium flash combined with mixing to the surface
by vigorous convection induced by the flash itself.

Solar and Stellar Astrophysics