J/A+A/667/A113 Tabulations for line-opacity calculation (Poniatowski+, 2022)
Method and new tabulations for flux-weighted line-opacity
and radiation line-force in supersonic media.
Poniatowski L.G., Kee N.D., Sundqvist J.O., Driessen F.A., Moens N.,
Owocki S.P., Gayley K.G., Decin L., de Koter A., Sana H.
<Astron. Astrophys. 667, A113 (2022)>
=2022A&A...667A.113P 2022A&A...667A.113P (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Opacities
Keywords: stars: early-type - stars: atmospheres - stars: winds, outflows -
stars: mass-loss - radiative transfer - hydrodynamics
Abstract:
In accelerating and supersonic media, the interaction of photons with
spectral lines can be of ultimate importance, especially in an
accelerating flow. However, fully accounting for such line forces is
computationally expensive and challenging, as it involves complicated
solutions of the radiative transfer problem for millions of
contributing lines. This currently can only be done by specialised
codes in 1-D steady-state flows. More general cases and higher
dimensions require alternative approaches. We presented a
comprehensive and fast method for computing the radiation line-force
using tables of spectral line-strength distribution parameters, which
can be applied in arbitrary (multi-D, time-dependent) simulations,
including those accounting for the line-deshadowing instability, to
compute the appropriate opacities. We assumed local thermodynamic
equilibrium (LTE) to compute a flux-weighted line opacity from
∼4 million spectral lines. We fitted the opacity computed from the
line-list with an analytic result derived for an assumed distribution
of the spectral line strength and found the corresponding
line-distribution parameters, which we here tabulated for a range of
assumed input densities ρ in [10-20, 10-10]g/cm3 and
temperatures T in [104, 104.7]K. We found that the variation of
the line distribution parameters plays an essential role in setting
the wind dynamics in our models. In our benchmark study, we also found
a good overall agreement between the O-star mass-loss rates of our
models and those derived from steady-state studies using more detailed
radiative transfer. Our models reinforce that self-consistent
variation of the line-distribution parameters is important for the
dynamics of line-driven flows. Within a well-calibrated O-star regime,
our results support the proposed methodology. In practice, utilising
the provided tables, yielded a factor >100 speed-up in computational
time compared to specialised 1-D model-atmosphere codes of line-driven
winds, which constitutes an important step towards efficient multi-D
simulations. We conclude that our method and tables are ready to be
exploited in various radiation-hydrodynamic simulations where the line
force is important.
Description:
The table presented gives the line strength distribution parameters
α, {bar}Q, Q0 and Thompson scattering mass absorption
coefficient κe. Each of these parameters is given as a
function of mass density ρ and temperature T of the gas. The table
was computed under the LTE assumption using the 'Munich' atomic
database (Pauldrach et al. 1998ASPC..131..258P 1998ASPC..131..258P, 2001A&A...375..161P 2001A&A...375..161P;
Puls et al. 2005A&A...435..669P 2005A&A...435..669P).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
ltetable.dat 143 400 Line strength distribution parameters and
Thompson scattering mass absorption coefficient
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Byte-by-byte Description of file: ltetable.dat
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Bytes Format Units Label Explanations
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1- 22 E22.16 [K] logT Temperature
25- 47 E23.16 [cm-2] logrho Density
50- 71 E22.16 --- alpha alpha parameter
74- 95 E22.16 --- barQ bar Q parameter
98-119 E22.16 --- Q0 Q0 parameter
122-143 E22.16 cm2/g kappa-e Thompson scattering mass absorption coefficient
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Acknowledgements:
Luka Poniatowski, luka.poniatowski(at)kuleuven.be
(End) Patricia Vannier [CDS] 21-Jul-2022