J/A+A/589/A21 K-H2 line shapes for cool brown dwarfs spectra (Allard+, 2016)
K-H2 line shapes for the spectra of cool brown dwarfs.
Allard N.F., Spiegelman F., Kielkopf J.F.
<Astron. Astrophys. 589, A21 (2016)>
=2016A&A...589A..21A 2016A&A...589A..21A (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Spectroscopy
Keywords: line: profiles - brown dwarfs
Abstract:
Observations of cooler and cooler brown dwarfs show that the
contribution from broadening at many bars pressure is becoming
important. The opacity in the red optical to near-IR region under
these conditions is dominated by the extremely pressure-broadened
wings of the alkali resonance lines, in particular, the KI resonance
doublet at 0.77um. Collisions with H2 are preponderant in brown
dwarf atmospheres at an effective temperature of about 1000K; the H2
perturber densities reach several 1019 even in Jupiter-mass planets
and exceed 1020 for super-Jupiters and older Y dwarfs. As a
consequence, it appears that when the far wing absorption due to
alkali atoms in a dense H2 atmosphere is significant, accurate
pressure broadened profiles that are valid at high densities of H2
should be incorporated into spectral models.
Description:
The relationship between the computed cross section and the normalized
absorption coefficient is:
I(Δω)=σ(Δω)/π*r0f where r0 is the
classical radius of the electron, and f is the oscillator strength of
the transition.
The far red wing is linearly dependent on H2 density for lower
density than 1021cm-3 and can be obtained from the following
tables for T=600, 820, 1000, 1500, 2000 and 3000K where
n(H2)=1021cm-3. For a more complete profile including the blue
wing, opacity tables are available on request from
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig8.dat 26 1413 Cross section of the red wing of the 4s-4p P3/2
of the KI resonance doublet perturbed by H2
fig9.dat 28 215 Cross section of the red wing of the 4s-4p P1/2
of the KI resonance doublet perturbed by H2
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Byte-by-byte Description of file: fig8.dat fig9.dat
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Bytes Format Units Label Explanations
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1- 4 I4 K T Temperature
7- 15 F9.7 um lambda Wavelength
17- 28 E12.5 cm-2 sigma Cross-section
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Acknowledgements:
Nicole Allard, nicole.allard(at)obspm.fr
(End) Patricia Vannier [CDS] 01-Apr-2016