7 Conclusion

Within the framework of the qualitative model presented here, which is a natural development of the general model presented in (Johansson & Letokhov 2001a), the anomalous intensity ratio between the close UV FeII spectral lines of a gas condensation (blob B) in the vicinity of the star $\eta$ Carinae can be explained without the need to introduce stimulated amplification. The model can further be verified by numerical calculatiions of narrow (a few tens or hundreds of cm^-1) resonances of the photoionization of the FeII ion from the quantum states $\rm c^{4}F_{7/2,9/2}$ near their photoionization limit. Finally, this work confirms the importance of the calculations by Hummer (1968) of the effect of continuous absorption on the observed intensity ratio between spectral lines in nebulae. Obviously, to create a quantitative model of the photoprocesses occurring in the gas condensations in the vicinity of $\eta$Car, it is necessary to compute the resonance transfer of the Ly$\alpha$radiation from the highly ionized HII region to the weakly ionized, optically denser HI region precisely in the inhomogeneous transition layer, i.e., in the neighborhood of the boundary of the Strömgren sphere.

Acknowledgements

One of the authors (V.L.) is very grateful to the Swedish Natural Science Research Council (NFR) for the T. Erlander Professorship-2000, which allows him to explore the "laser-like'' atomic physics with Hubble Space Telescope data in the stimulating atmosphere of Lund University. The project is also supported by grants (S.J.) from the Swedish National Space Board and the Crafoord Foundation. The authors are also grateful to the anonymous referee for valuable comments and criticism.