J/A+A/683/A188 Stellar atmosphere opacity K broadened by He (Allard+, 2024)
New theoretical study of potassium perturbed by He and comparison to laboratory
spectra.
Allard N.F., Kielkopf J.F., Myneni K., Blakely J.N.
<Astron. Astrophys. 683, A188 (2024)>
=2024A&A...683A.188A 2024A&A...683A.188A (SIMBAD/NED BibCode)
+2025A&A...694C..10A 2025A&A...694C..10A
ADC_Keywords: Atomic physics
Keywords: atomic data - atomic processes - line: formation - molecular data -
opacity - brown dwarfs
Abstract:
The visible and near-infrared spectra of late L- and T-type dwarf
stars are dominated in large part by the resonance lines of neutral Na
and K. It is the collision broadening of these atomic lines by H2
and He in the stellar atmosphere that determines the continuum from
below 0.5um to above 0.9um in the spectrum. Their line profiles can be
detected as far as 3000cm-1 from the line center in T dwarfs and
consequently an accurate and detailed determination of the complete
profile, including the extreme far wing, is required to model the
contribution of these strong alkali resonance lines to brown dwarf
spectra. We report on our new calculations of unified line profiles of
K perturbed by He using ab initio potential data for the conditions
prevailing in cool substellar brown dwarfs and hot dense planetary
atmospheres with temperatures from Teff=500 to 3000K. For such objects
with atmospheres of H2 and He, conventional laboratory absorption
spectroscopy can be used to examine the line wings and test the line
shape theories and molecular potentials. We find that an analytical
Lorentzian profile is useful for a few cm-1 from the line center,
but not in the line wings, where the radiative transfer is a
consequence of the K-He radiative collisions that are sensitive to
the interaction potentials. Tables of the K-He absorption coefficients
of the resonance lines allow accurate model atmospheres and synthetic
spectra. For this purpose, we present new opacities from comprehensive
line shape theory incorporating accurate ab initio potentials. Use of
these new tables for the modeling of emergent spectra will be an
improvement over previous line shape approximations based on
incomplete or inaccurate potentials. We also present Lorentzian impact
parameters obtained in the semi-classical and quantum theory for the K
4s-4p resonance line centered at 0.77um specifically for the line core
regime.
Description:
File README.pdf contains all explanations of the files.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
README.pdf 512 127 (non-integer number of records ?)
D1/* . 8 Tables of opacities, D1 components
D2/* . 8 Tables of opacities, D2 components
(corrected files from erratum, 11/02/2024)
lect_sig.csh 25 34 Shell script will run under Bash
(or the tcsh or csh shells)
lect_sig.f 76 178 Fortran program will read a 'table' file and
produce a 'sigma' file
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Acknowledgements:
Nicole Allard, nicole.allard(at)obspm.fr
History:
19-Mar-2024: on-line version
11-Feb-2025: corrected file tableD2KHe8001e212025.omg in D2 subdirectory
(End) Patricia Vannier [CDS] 27-Dec-2023