Loving ISIS - Confessions of a Former XSPEC User
ISIS started out as a Chandra
gratings/wavelength-centric program; however, it evolved to become
much more than that. This heritage as a Chandra gratings analysis
tool shows up in some ways, while its design philosophy as a
powerfully scripted program and the fact that all ISIS commands are
These latter two default behaviors can be overridden via choices made
in a standard start-up file. Specifically, create in your home
directory a file called
Isis_Append_Semicolon=1; Isis_Use_PHA_Grouping=1;Throughout the examples presented here, however, we'll retain the semi-colon, and since we will be rebinning the data anyhow, we will ignore the default PHA grouping in the file. The
To help familiarize users with these differences, on these web pages I give a detailed example of an ISIS analysis of a set of simultaneous radio and RXTE X-ray observations. The former is stored as an ASCII file giving frequency in Hz and radio flux (with its, presumed gaussian, error) in units of mJy. The latter consists of both PCA and HEXTE data, stored as FITS files, taken from the usual RXTE data extraction procedures. The data can be obtained as a gzipped tar file found here.
A plot of the data is shown below. A detailed description of the
observations can be found in
et al. (2005), ApJ, 626, p. 1006. (Every figure and result in that
paper was generated with ISIS.)
All spectral fit results and figures found on these web pages were
generated with this analysis script.
This script presumes that you have downloaded my
Next up: Five ISIS Basics.
This page was last updated Oct 7, 2013 by Michael Nowak. To comment on it or the material presented here, send email to email@example.com.