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A method to estimate the effect of line blanketing in NLTE radiative transfer calculations
We present a method to estimate the contribution of line opacity to the total opacity as a function of wavelength. The estimated line-opacity function can then be used to simulate line-blanketing in NLTE radiative transfer calculations. Given a reference flux distribution (either observed or theoret...
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Published in: | Astronomy and astrophysics (Berlin) 2001-07, Vol.373 (3), p.993-997 |
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Main Authors: | , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | We present a method to estimate the contribution of line opacity to the total opacity as a function of wavelength. The estimated line-opacity function can then be used to simulate line-blanketing in NLTE radiative transfer calculations. Given a reference flux distribution (either observed or theoretical), our method allows to obtain a good estimate of the spectrum without the need for considering in detail all the millions of lines contributing to line blanketing. We applied the method to the spectra computed from a sample of photospheric models with effective temperatures $T_\mathrm{eff}$ $= 4200$, 5200 and 6200 K, $\log g$ $= 4.0$, 4.5, 5.0 and [A/H] $= 0.0$, -1.0, -2.0, taken from the NextGen database (Allard & Hauschildt [CITE]). The computed flux distributions agree quite well with the corresponding LTE line-blanketed NextGenfluxes when we introduce the estimated line-opacity contribution as a multiplicative factor of the continuum opacity in the radiative transfer calculations. In particular we discuss the importance of a correct estimate of the continuum flux, mainly in the UV, in the NLTE formation of the Caii H & K, the Caii InfraRed Triplet (IRT: $\lambda=$ 8498, 8542, 8662), Nai D, Lii and Ki resonance lines. |
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ISSN: | 0004-6361 1432-0746 |
DOI: | 10.1051/0004-6361:20010661 |