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Titolo: A model for the origin of the anomalous and very bright UV lines of FeII in gaseous condensations of the star eta Carinae
Autore: Johansson, S; Letokhov, VS;
- Indirizzi:
- Lund Univ, Dept Phys, S-22100 Lund, Sweden Lund Univ Lund Sweden S-22100Lund Univ, Dept Phys, S-22100 Lund, Sweden Russian Acad Sci, Inst Spect, Troitsk 142190, Moscow Region, Russia Russian Acad Sci Troitsk Moscow Region Russia 142190 oscow Region, Russia
- Titolo Testata:
- ASTRONOMY & ASTROPHYSICS
fascicolo: 1,
volume: 378,
anno: 2001,
pagine: 266 - 278
- SICI:
- 1432-0746(200110)378:1<266:AMFTOO>2.0.ZU;2-X
- Fonte:
- ISI
- Lingua:
- ENG
- Soggetto:
- EJECTA; SPECTRUM;
- Keywords:
- atomic processes; line : formation; radiation mechanisms : non-thermal; stars : individual : eta Carinae;
- Tipo documento:
- Article
- Natura:
- Periodico
- Settore Disciplinare:
- Physical, Chemical & Earth Sciences
- Citazioni:
- 23
- Recensione:
- Indirizzi per estratti:
- Indirizzo: Johansson, S Lund Univ, Dept Phys, POB 118, S-22100 Lund, Sweden Lund UnivPOB 118 Lund Sweden S-22100 , S-22100 Lund, Sweden
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- Citazione:
- S. Johansson e V.S. Letokhov, "A model for the origin of the anomalous and very bright UV lines of FeII in gaseous condensations of the star eta Carinae", ASTRON ASTR, 378(1), 2001, pp. 266-278
Abstract
We present a qualitative physical model of the origin of two very bright UV lines of Fe II at 2507-2509 Angstrom, 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 HLy alpha 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 HLy alpha, which makes it possible to selectively photo-excite short-lived (approximate to1 ns) states at 11.2 eV in Fe II. Within the frame of the present model the intense HLy alpha radiation induces a depletion of the lower, long-lived (approximate to1 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 HLy alpha 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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Documento generato il 20/05/13 alle ore 00:53:10