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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
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:
FileName Lrecl Records Explanations
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/* 0 15 Original files with readme
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
Bytes Format Units Label Explanations
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
Byte-by-byte Description of file: set.dat
Bytes Format Units Label Explanations
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)
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.
Byte-by-byte Description of file: opac.dat
Bytes Format Units Label Explanations
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)
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.
Acknowledgements: Michael T. Lederer, lederer(at)astro.univie.ac.at
(End) M. Lederer [Vienna Univ., Austria], P. Vannier [CDS] 14-Nov-2008
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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