He-like Line Emissivity Modifier - ISIS/APED density dependent emissivities
NOTE: This page will be removed soon and replaced by a greatly improved version! (which will include photoexcitation dependence for OB-star modeling) [2011.02.15]
About the emissivity modifier for He-like tripletsThe He-like triplet lines which occur in the X-ray band from 5-42A are powerful diagnostics of density or photoexcitation. The APED (Astrophysical Plasma Emission Database), however, only contains emissivities for low density. To use triplet lines as a density diagnostic, one method is to fit the line strengths and from the ratio of the forbidden to intercombination line fluxes (f/i), then look up the implied density from external sources. To provide better support for more direct fitting and modeling, we have
Further details can be found in this document.
Important FilesTwo files are required to implement the emissivity modifiers within ISIS in conjunction with APED: a FITS file which tabulates emissivity modifier coefficients for He-like triplets, and an ISIS source code file which defines the modifier fit function:
InstallationPut the source file, he_modifier.sl, somewhere in your ISIS load path and put the data file in the same place. The default location for the data file is the same directory as the source code.
ExamplesAn ISIS test script, t_he_modifier.sl, demonstrates several ways to use the He-like triplet modifiers. The script is heavily commented, and produces the following graphics:
This page was last updated Feb 15, 2011 by David P. Huenemoerder. To comment on it or the material presented here, send email to email@example.com.