Issue |
A&A
Volume 385, Number 1, April I 2002
|
|
---|---|---|
Page(s) | 313 - 327 | |
Section | Astronomical instrumentation | |
DOI | https://doi.org/10.1051/0004-6361:20020059 | |
Published online | 15 April 2002 |
The origin of the anomalous intensity ratio between very bright UV FeII lines and their satellites in gaseous condensations close to the star η Carinae
1
P.N. Lebedev Physical Institute, Russian Academy of Sciences, 53 Leninsky Prospect, Moscow 117294, Russia
2
Atomic Astrophysics, Lund Observatory, Lund University, PO Box 43, Lund 221 00, Sweden
3
Institute of Spectroscopy, Russian Academy of Sciences, Troitsk 142190, Moscow region, Russia e-mail: vladilen.letokhov@astro.lu.se
Corresponding author: S. Johansson, sveneric.johansson@astro.lu.se
Received:
12
July
2001
Accepted:
14
January
2002
We present a model that explains the anomalous intensity ratios between
each of two very bright UV lines of Fe II at 2507 Å and 2509 Å
and its corresponding satellite line, observed in HST spectra of
a compact gaseous condensation (blob B) in the vicinity of the star Car.The model is based on the assumption that the FeII transitions have a substantial
optical thickness, which varies as a result of the photodepletion of the
long-lived lower states, c4F
, by the intense
Lyα radiation. In conditions where the photodepletion rates of these
two states differ, the resonance scattering lengths of the spectral lines
become different as well. In the presence of a weak, nonresonant (continuous)
absorption, this gives rise to a difference in attenuation between the spectral
lines (the Hummer effect (Hummer 1968)). It is the combination of these
two effects that explains the anomalous (as compared with laboratory data)
intensity ratios observed in the two pairs of UV FeII lines. Ionization channels of
stimulated photodepletion by the Lyα radiation, including the possible role
of autoionization levels, are considered.
Key words: atomic processes / line: formation / radiation mechanisms: non-thermal / stars: individual: η Carinae
© ESO, 2002
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.