  We report the first identification of forbidden line components from an
element heavier than helium in the spectrum of astrophysical plasmas. As yet,
these components were identified only in laboratory plasmas and not in
astrophysical objects. Forbidden components are well known for neutral helium
lines in hot stars, particularly in helium-rich post-AGB stars and white
dwarfs. We discovered that two hitherto unidentified lines in the ultraviolet
spectra of hot hydrogen-deficient (pre-) white dwarfs can be identified as
forbidden line components of triply ionized carbon (C IV). The forbidden
components (3p-4f and 3d-4d) appear in the blue and red wings of the strong,
Stark broadened 3p-4d and 3d-4f lines at 1108 Angstroem and 1169 Angstroem,
respectively. They are visible over a wide effective temperature range
(60,000-200,000 K) in helium-rich (DO) white dwarfs and PG1159 stars that have
strongly oversolar carbon abundances.
