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The origin of the anomalous intensity ratio between very bright UV FeII lines and their satellites in gaseous condensations close to the star eta Carinae

Klimov, V; Johansson, Sveneric LU and Letokhov, Vladilen LU (2002) In Astronomy & Astrophysics 385(1). p.313-327
Abstract
We present a model that explains the anomalous intensity ratios betweeneach of two very bright UV lines of Fe II at 2507 Å and 2509Å and its corresponding satellite line, observed in HST spectra ofa compact gaseous condensation (blob B) in the vicinity of the starprotect eta Car.The model is based on the assumption that the FeIItransitions have a substantial optical thickness, which varies as aresult of the photodepletion of the long-lived lower states,c<SUP>4</SUP>F<SUB>7/2,9/2</SUB>, by the intense Lyalpha radiation. Inconditions where the photodepletion rates of these two states differ,the resonance scattering lengths of the spectral lines become differentas well. In the presence of a weak, nonresonant... (More)
We present a model that explains the anomalous intensity ratios betweeneach of two very bright UV lines of Fe II at 2507 Å and 2509Å and its corresponding satellite line, observed in HST spectra ofa compact gaseous condensation (blob B) in the vicinity of the starprotect eta Car.The model is based on the assumption that the FeIItransitions have a substantial optical thickness, which varies as aresult of the photodepletion of the long-lived lower states,c<SUP>4</SUP>F<SUB>7/2,9/2</SUB>, by the intense Lyalpha radiation. Inconditions where the photodepletion rates of these two states differ,the resonance scattering lengths of the spectral lines become differentas well. In the presence of a weak, nonresonant (continuous) absorption,this gives rise to a difference in attenuation between the spectrallines (the Hummer effect (Hummer 1968)). It is the combination of thesetwo effects that explains the anomalous (as compared with laboratorydata) intensity ratios observed in the two pairs of UV FeII lines.Ionization channels of stimulated photodepletion by the Lyalpharadiation, including the possible role of autoionization levels, areconsidered. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
ATOMIC PROCESSES, LINE: FORMATION, RADIATION MECHANISMS: NON-THERMAL, STARS: INDIVIDUAL: ETA CARINAE
in
Astronomy & Astrophysics
volume
385
issue
1
pages
313 - 327
publisher
EDP Sciences
external identifiers
  • wos:000174626200029
  • scopus:0036534271
ISSN
0004-6361
DOI
10.1051/0004-6361:20020059
language
English
LU publication?
yes
id
a5e7a5b8-d1bc-4ced-b284-07f4ab7d6e7c (old id 130379)
date added to LUP
2007-07-13 13:39:38
date last changed
2017-09-03 04:37:38
@article{a5e7a5b8-d1bc-4ced-b284-07f4ab7d6e7c,
  abstract     = {We present a model that explains the anomalous intensity ratios betweeneach of two very bright UV lines of Fe II at 2507 Å and 2509Å and its corresponding satellite line, observed in HST spectra ofa compact gaseous condensation (blob B) in the vicinity of the starprotect eta Car.The model is based on the assumption that the FeIItransitions have a substantial optical thickness, which varies as aresult of the photodepletion of the long-lived lower states,c&lt;SUP&gt;4&lt;/SUP&gt;F&lt;SUB&gt;7/2,9/2&lt;/SUB&gt;, by the intense Lyalpha radiation. Inconditions where the photodepletion rates of these two states differ,the resonance scattering lengths of the spectral lines become differentas well. In the presence of a weak, nonresonant (continuous) absorption,this gives rise to a difference in attenuation between the spectrallines (the Hummer effect (Hummer 1968)). It is the combination of thesetwo effects that explains the anomalous (as compared with laboratorydata) intensity ratios observed in the two pairs of UV FeII lines.Ionization channels of stimulated photodepletion by the Lyalpharadiation, including the possible role of autoionization levels, areconsidered.},
  author       = {Klimov, V and Johansson, Sveneric and Letokhov, Vladilen},
  issn         = {0004-6361},
  keyword      = {ATOMIC PROCESSES,LINE: FORMATION,RADIATION MECHANISMS: NON-THERMAL,STARS: INDIVIDUAL: ETA CARINAE},
  language     = {eng},
  number       = {1},
  pages        = {313--327},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {The origin of the anomalous intensity ratio between very bright UV FeII lines and their satellites in gaseous condensations close to the star eta Carinae},
  url          = {http://dx.doi.org/10.1051/0004-6361:20020059},
  volume       = {385},
  year         = {2002},
}