Xspec Version 11.3 Release Notes
November 26^{th} 2003
V11.3 is an incremental release over V11.2.
The following list summarizes the major changes to XSPEC since the
previous edition of the user's manual. Bug fixes are listed in Appendix E.
 Commands
 Added new option "xset forcecalc on/off" to force calculation of the model
for all datasets. This is required for mixing models.
 Added the following new options to "tclout" : ftest, query, response, arf,
backgrnd, xflt, areascal, backscal, expos
 If "steppar" is run with a single parameter then followed by "plot contour"
a plot of statistic vs. parameter value will be produced.
 The model description written as part of the standard output at the end of
a fit can now be cutandpasted directly into the "editmod" command.
 The commands "datafile{n}" and "arf{n}" can now mean n1th extension
following the first spectral extension. This only works for type I spectral
extensions. If the first spectral extension is type II then the commands
have their usual interpretation as the nth spectrum in the extension.
 When using the Cstatistic the command "plot chisq" now gives contributions
to C shown either +ve or ve depending on the sign of datamodel.
 There is a new option to the command "log filename" to add to the filename
a string giving a date and time stamp.
 Models
 New Models:
 acisabs
 the absorption due to the contamination on ACIS. Should only be
used with response matrices that do not have this effect included!
 bkn2pow
 a threesegment broken powerlaw.
 expdec
 simple exponential decay model.
 nsa
 neutron star H atmosphere model with different values of magnetic field.
 pwab
 absorption with a powerlaw distribution of covering fraction.
 smaug
 deprojection model for an extended an opticallythin source (eg a
cluster).
 xmmpsf
 model to mix spectra between regions to take into account XMMNewton PSF.
 Model Changes
 The command "xset APECROOT" can now take an argument giving just the APEC
version number. The default has been updated to 1.3.1.
 The projct model works correctly for multiple datasets.
 The mekal cooling flow models now come in two versions. The default version
has a variable number of emission measure steps that can be set using the
command "xset cflow_ntemps" followed by a number. The old version of the
models, which included a bug, are available by setting "xset cflow_version 1".
 General
 The "ignore" command runs much faster on spectra with big response matrices.
 The screen output from "error" now also includes the parameter range in
terms of plus and minus difference from the best fit.
 The abundance tables have been extended to include all elements up to Zn.
 The abundance table and crosssection in use have been added to (auto)save.
 The default cosmology has been set to the "WMAP standard" of H0=70,
Lambda=0.73 in a flat Universe.
 MarkovChain Monte Carlo Fitting Algorithm

Preliminary code for Markov Chain Monte Carlo is included. The "chain"
command runs MCMC chains and the results can be displayed using "plot mcmc".
This is still in the experimental stage. At the moment it seems to work
reasonably well if a fit is done then chains run to generate the posterior
probability distribution. The aim is to improve this so that it is not
necessary to first find the minimum.
 Version 11.2 Release Notes
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Last modified: Friday, 09Apr2004 12:00:52 EDT
