A model for the origin of the anomalous and very bright UV lines of Fe II in gaseous condensations of the star η Carinae

Details A model for the origin of the anomalous and very bright UV lines of Fe II in gaseous condensations of the star η Carinae A model for the origin of the anomalous and very bright UV lines of Fe II in gaseous condensations of the star η Carinae

Oct 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001a%26a...378..266j&link_type=abstract

Astronomy and Astrophysics, v.378, p.266-278 (2001)

Astronomy and Astrophysics

Astrophysics

16

Atomic Processes, Line: Formation, Radiation Mechansims: Non-Thermal, Stars: Individual: Eta Carinae

Scientific paper

We present a qualitative physical model of the origin of two very bright UV lines of Fe II at 2507-2509 Å, present in high-resolution spectra of gaseous condensations (blobs) close to the central star of eta Carinae. The spectra have been obtained with the Hubble Space Telescope (HST). The model is based on a type of Bowen mechanism with selective photoexcitation of Fe II by a broad HLyalpha profile, generated in the HII region and diffusely transferred to the optically thick HI region. The frequency distribution by large Doppler diffusion into the HI region provides a substantial broadening of HLyalpha , which makes it possible to selectively photo-excite short-lived (~1 ns) states at 11.2 eV in Fe II. Within the frame of the present model the intense HLyalpha radiation induces a depletion of the lower, long-lived (~1 ms) level of the strong UV lines by photoionization. The subsequent recombination of Fe III explains the appearance of the ``forest'' of narrow Fe II lines. The possibility of a cyclic process is also discussed, where HLyalpha induces depletion to bound states, which have fast decays in the far-UV to the lower state of the Bowen pumping channel.

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