J/A+A/494/403 Low temperature Rosseland opacities (Lederer+, 2009)
Low temperature Rosseland opacities with varied abundances of carbon and
nitrogen.
Lederer M.T., Aringer B.
<Astron. Astrophys. 494, 403 (2009)>
=2009A&A...494..403L 2009A&A...494..403L
ADC_Keywords: Atomic physics; Models, atmosphere ; Opacities; Abundances
Keywords: radiative transfer - molecular data - stars: evolution
Abstract:
We provide low temperature opacity data that incorporate varied
abundances of the elements carbon and nitrogen. In the temperature
range that we focus at, molecules are the dominant opacity source.
Our dataset spans a large metallicity range and shall deliver the
necessary input data for stellar evolution models as well as other
applications. We conduct chemical equilibrium calculations in order to
evaluate the partial pressures of neutral atoms, ions and molecules.
Based on a large dataset containing atomic line and continuum data,
and, most importantly, a plethora of molecular lines, we subsequently
calculate Rosseland mean opacity coefficients. This is done not only
for a number of different metallicities, but also for varied
abundances of the isotopes 12C and 14N at each metallicity. The
molecular data comprise the main opacity sources at either an
oxygen-rich or carbon-rich chemistry. We tabulate the opacity
coefficients as a function of temperature and, basically, density.
Already within a certain chemistry regime an alteration in the carbon
abundance causes, due to the special role of the CO molecule,
considerable changes in the Rosseland opacity. The transition from a
scaled solar (i.e. oxygen-rich) mixture to the carbon-rich regime
results in opacities that can, at low temperatures, be orders of
magnitude different compared to the initial situation. The reason is
that different molecular absorbers make up the mean opacity in either
case. A varying abundance of nitrogen has less pronounced effects but,
nevertheless, cannot be neglected.
Description:
The database of Rosseland opacities consists of 14 files
(kR_Z?E-?.dat), one for each metallicity. The available values of the
metallicity are listed in the file kRZfCN.dat together with the
respective enhancement factors for 12C and 14N. This file contains
information equivalent to Table 3 from the paper. The data files
consist of a header indicating the abundances used (Lodders,
2003ApJ...591.1220), the initial metallicity, the initial mass
fractions for 12C, 14N and the alpha elements, and a look-up table
for the actual data block. This block is made up of 63 rectangular
data arrays where the logarithm of the Rosseland opacity (logκR
[cm2/g]) is tabulated as a function of the logarithm of the gas
temperature (logT [K]) and the logarithm of R (logR [g/cm3/K31018]
with R=ρ/(T6)3 and T6=T/(106K)). The ranges covered are
3.2≤logT≤4.05 with a step size of 0.05, and -7.0≤logR≤1.0 with a
step size of 0.5. The 63 tables result from the variation of the
hydrogen mass fraction (X=0.5,0.7,0.8), and the mass fractions
X(12C) [7 different values] and X(14N) [3 different values]. The
tables are ordered such that the mass fraction X(12C) varies fastest
followed by the hydrogen mass fraction and X(14N). The original
files are available in files subdirectory. For future compatibility a
data field for the alpha element enhancement factor was introduced in
the look-up table.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 87 14 Metallicities contained in the database and
respective enhancement factors for C and N
set.dat 78 882 Set of initial parameters
opac.dat 133 15876 Rosseland opacity coefficients
files/* . 15 Original files with readme
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See also:
VI/80 : Opacities from the Opacity Project (Seaton+, 1995)
VI/89 : Radiative forces for stellar envelopes (Seaton, 1997)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 7 F7.5 --- Z Metallicity (mass fraction)
9- 15 F7.1 --- fC1 1st carbon enhancement factor
17- 23 F7.1 --- fC2 2nd carbon enhancement factor
25- 31 F7.1 --- fC3 3rd carbon enhancement factor
33- 39 F7.1 --- fC4 4th carbon enhancement factor
41- 47 F7.1 --- fC5 5th carbon enhancement factor
49- 55 F7.1 --- fC6 6th carbon enhancement factor
57- 63 F7.1 --- fC7 7th carbon enhancement factor
65- 71 F7.1 --- fN1 1st nitrogen enhancement factor
73- 79 F7.1 --- fN2 2nd nitrogen enhancement factor
81- 87 F7.1 --- fN3 3rd nitrogen enhancement factor
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Byte-by-byte Description of file: set.dat
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Bytes Format Units Label Explanations
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1- 5 E5.1 --- Zinit Initial metallicity
7- 8 I2 --- Set [1/63] Set number
12- 14 F3.1 --- X Hydrogen mass fraction (X)
18- 25 F8.6 --- Y Helium mass fraction (Y)
29- 36 F8.6 --- Z Metal mass fraction (Z)
41- 48 F8.3 --- C/O C/O ratio
52- 58 F7.1 --- 12C Carbon (12C) enhancement factor
62- 68 F7.1 --- 14N Nitrogen (14N) enhancement factor
72- 78 F7.1 --- alpha [1.0] Alpha elements enhancement factor (1)
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Note (1): Note on the alpha elements enhancement factor: this factor is
always 1 in the current version of the database. It was introduced
for future compatibility.
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Byte-by-byte Description of file: opac.dat
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Bytes Format Units Label Explanations
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1- 5 E5.1 --- Zinit Initial metalicity
7- 8 I2 --- Set [1/63] Set number for initial values (1)
10- 14 F5.3 [K] logT logT value
16- 21 F6.3 [---] kR-7.0 log(Rosseland opacity) for logR=-7.0, logT (2)
23- 28 F6.3 [---] kR-6.5 log(Rosseland opacity) for logR=-6.5, logT (2)
30- 35 F6.3 [---] kR-6.0 log(Rosseland opacity) for logR=-6.0, logT (2)
37- 42 F6.3 [---] kR-5.5 log(Rosseland opacity) for logR=-5.5, logT (2)
44- 49 F6.3 [---] kR-5.0 log(Rosseland opacity) for logR=-5.0, logT (2)
51- 56 F6.3 [---] kR-4.5 log(Rosseland opacity) for logR=-4.5, logT (2)
58- 63 F6.3 [---] kR-4.0 log(Rosseland opacity) for logR=-4.0, logT (2)
65- 70 F6.3 [---] kR-3.5 log(Rosseland opacity) for logR=-3.5, logT (2)
72- 77 F6.3 [---] kR-3.0 log(Rosseland opacity) for logR=-3.0, logT (2)
79- 84 F6.3 [---] kR-2.5 log(Rosseland opacity) for logR=-2.5, logT (2)
86- 91 F6.3 [---] kR-2.0 log(Rosseland opacity) for logR=-2.0, logT (2)
93- 98 F6.3 [---] kR-1.5 log(Rosseland opacity) for logR=-1.5, logT (2)
100-105 F6.3 [---] kR-1.0 log(Rosseland opacity) for logR=-1.0, logT (2)
107-112 F6.3 [---] kR-0.5 log(Rosseland opacity) for logR=-0.5, logT (2)
114-119 F6.3 [---] kR+0.0 log(Rosseland opacity) for logR=+0.0, logT (2)
121-126 F6.3 [---] kR+0.5 log(Rosseland opacity) for logR=+0.5, logT (2)
128-133 F6.3 [---] kR+1.0 log(Rosseland opacity) for logR=+1.0, logT (2)
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Note (1): Initial abundances values are in set.dat files,
for Zinit and Set values.
Note (2): R = ρ/(T6)3 where T6=T/106, expressed in g/cm3/MK3.
The 18 values of logT are:
3.200, 3.250, 3.300, 3.350, 3.400, 3.450, 3.500, 3.550, 3.600, 3.650,
3.700, 3.750, 3.800, 3.850, 3.900, 3.950, 4.000, 4.050
The 17 values of logR are:
-7.000, -6.500, -6.000, -5.500, -5.000, -4.500, -4.000, -3.500,
-3.000, -2.500, -2.000, -1.500, -1.000, -0.500, 0.000, 0.500, 1.000
In symbolic form the Rosseland opacities as a function of
logT and logR are arranged in rectangular arrays like that:
##########################
log R
log T -7.000 ... 1.000
3.200 ##.### ##.### ##.###
... ##.### ##.### ##.###
4.050 ##.### ##.### ##.###
The respective opacity coefficient (represented by ##.###) is located
at the crossing point of the log R vs. log T grid.
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Acknowledgements:
Michael T. Lederer, lederer(at)astro.univie.ac.at
(End) M. Lederer [Vienna Univ., Austria], P. Vannier [CDS] 14-Nov-2008