The ATOMDB contains three separate types of spectral output, in addition to the raw atomic data stored in FITS files in the APED directory (For a description of the atomic data formats used in APED, see this paper.) These three additional files, which are calculated by APEC, are:
Files with the suffix _line.fits are FITS files with one block (HDU) for each temperature, along with an initial parameter block that gives the complete list of temperatures and densities found in the file. The data blocks contain the following columns:
Lambda | The best available wavelength (in Angstroms) |
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Lambda_Err | If available, the best estimate of the wavelength error (in Angstroms). If no value is available (ie, only theoretical calculations exist with no error estimate given), this is set to NaN |
Epsilon | The line emissivity at the temperature and density of the block (in photons cm^3 s^-1) |
Epsilon_Err | Available for future expansion; currently set to NaN. |
Element | The atomic number Z of the element |
Ion | The integer value of roman numeral describing the ion stage. I.e., 1 for a neutral ion, 2 for singly-ionized. |
UpperLev | The upper level of transition, keyed to the relevant energy level file in the APED. |
LowerLev | The lower level of transition, keyed to energy level file in APED. |
Files with the suffix _linelist.fits are FITS files with two data blocks, each with the same number of rows. The first block gives each line and its peak emissivity value, and the second block contains vector columns that give the values at each temperature and density. This is frequently the more useful file when browsing using prism. The columns in this file are:
Lambda | The best available wavelength (in Angstroms) |
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Lambda_Err | If available, the best estimate of the wavelength error (in Angstroms). If no value is available (ie, only theoretical calculations exist with no error estimate given), this is set to NaN |
LambdaTh | The theoretical wavelength; superceded by the value in Lambda if it is different. |
dLambdaTh | Error in the theoretical wavelength, iv available. If not available, set to NaN |
Element | The atomic number Z of the element |
Ion | The integer value of roman numeral describing the ion stage. I.e., 1 for a neutral ion, 2 for singly-ionized. |
UpperLev | The upper level of transition, keyed to the relevant energy level file in the APED. |
LowerLev | The lower level of transition, keyed to energy level file in APED. |
ArraySize | The number of elements in the temperature and emissivity vectors |
PeakIndex | The index of the peak emissivity in the emissivity vector. |
Temperature | Vector of temperatures, in Kelvin, with significant emission in the line. |
Density | Vector of densities with significant emission in the line |
Emissivity | Vector of emissivities (in photons cm^3 s^-1) |
EmissivityErr | Available for future expansion; currently set to NaN. |
A compressed continuum file has a name ending in _coco.fits. and it contains the following columns:
Z | The element's atomic number |
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rmJ | The ion of interest, from the roman numeral value; ie 6 for VI |
N_Cont | The length of the continuum vector |
E_Cont | A vector containing energies, in keV, where the continuum value is calculated |
Continuum | A vector containing the continuum, in phot cm^3 s^-1 keV^-1, at the energies listed in the E_cont vector |
Cont_Err | currently not used |
N_Pseudo | The length of the pseudo-continuum vector; the pseudo-continuum consists of lines which are too weak to list individually and so are stored here so that they may contribute to the total spectrum without taking up too much space |
E_Pseudo | A vector containing energies, in keV, where the pseudo-continuum value is calculated |
Pseudo | A vector containing the pseudo-continuum, in phot cm^3 s^-1 keV^-1, at the energies listed in the E_cont vector |
Pseudo_Err | currently not used |