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Xspec Version 11.3 Release Notes


November 26th 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 cut-and-pasted directly into the "editmod" command.

    • The commands "datafile{n}" and "arf{n}" can now mean n-1th 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 C-statistic the command "plot chisq" now gives contributions to C shown either +ve or -ve depending on the sign of data-model.

    • 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 three-segment broken power-law.
      expdec
      simple exponential decay model.
      nsa
      neutron star H atmosphere model with different values of magnetic field.
      pwab
      absorption with a power-law distribution of covering fraction.
      smaug
      deprojection model for an extended an optically-thin source (eg a cluster).
      xmmpsf
      model to mix spectra between regions to take into account XMM-Newton 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 cross-section 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.

  • Markov-Chain 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.
    • O
    Version 11.2 Release Notes

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    Last modified: Friday, 09-Apr-2004 12:00:52 EDT