One of the puzzles discovered in the course of
high-spectral-and-spatial-resolution observations of the star 
Carinae
with the Hubble Space
Telescope was anomalous (other than predicted by laboratory data) intensity ratios
between two very bright narrow FeII lines at 2507 Å
and 2509 Å and their satellites. This observation was so extraordinary
that it even gave rise to the assumption of stimulated amplification of
these lines (Johansson et al. 1996). In a recent report (Johansson &
Letokhov 2001b), we have
analyzed a number of photoprocesses induced by the intense Ly
radiation in a gaseous blob (blob B, see below) in the immediate vicinity of
the star
Car. These processes
can, in principle, help to qualitatively describe all these anomalous effects
within the framework of the physical parameters estimated for
Car and its
blobs (Davidson & Humphreys 1971; Davidson 1999; Hamann et al. 1999).
Using all these facts as the base, we have
considered (Johansson & Letokhov 2001b) a three-zone blob model including an active HII
region (which generates Ly
photons), an intermediate passive HI
region (which broadens the Ly
spectral line because of
Doppler diffusion), and a passive HI + FeII region, in which the broadened
Ly
radiation can excite FeII ions and thus cause the abnormal UV
fluorescence observed. Moreover, this model predicts a significant optical
thickness for the FeII transitions at
2507, 2509, which can
explain the anomalous intensity ratio between these bright UV lines and their
satellites. In the present paper, we develop this model further, so that this
anomaly can be explained without the need to exploit the idea of stimulated
amplification of the corresponding transitions.
Before going on to the main subject of this paper, let us formulate the main features
of the model presented earlier (Johansson & Letokhov 2001a,b) of the origin of
the extremely bright UV lines of FeII in the gaseous condensations near the star
Carinae.
Copyright ESO 2002