XSPEC v12.8.1 released as part of HEAsoft 6.14

The latest release of XSPEC is now available from the usual place. The release notes are as follows :

New features:

- New models:
     cpflux  - a variant of cflux for photon flux.
     heilin  - Voigt absorption profiles for the HeI series
     lyman   - Voigt absorption profiles for the HI or HeII series
     zbabs   - EUV ISM attenuation

- A new statistic, pgstat, has been added for the case of Poisson-distributed
  data
  with a Gaussian-distributed background. The whittle statistic can
  now be used when fitting averaged power density functions by
  appending an integer (so eg whittle5 is the statistic to use when
  fitting a pdf constructed by averaging those from 5 observations).

- The old CERN Minuit library, which is used for the migrad, minim, monte,
  and simplex fitting methods and the improve command, has been
  replaced by the new version. The minim and monte methods are no
  longer supported and the new version does not include an improve command.
  The output from the migrad and simplex fitting methods now looks the
  same as that from the leven method. Note however that the rules for
  when to write intermediate fit results are not directly comparable
  so do not provide a measure of the relative speed of the methods.

- Fakeit now has a 'nowrite' option to generate fake spectra without
  producing output files.  This is also now available in the
  multifake.tcl script command.

- Parallel processing capability has been added to the steppar command
  and can be invoked using the parallel command.

- Markov Chain Monte Carlo (the chain command) now uses the
  Goodman-Weare algorithm by default. Previously the default was
  Metropolis-Hastings.

- After a chain run, the best-fit parameters and statistic are now
  displayed with "chain info", and are available through the "tclout
  chain" option.

- The default atom_db version used in apec models may now be modified
  with the ATOMDB_VERSION keyword in the user's Xspec.init file.

- Steppar now has a 'delta' option for performing grids centered on
  the best-fit parameters.

- The 'setplot delete' option has been enhanced to allow removal of all
  or a range of commands.

- For external programs calling XSPEC, new wrapper functions have been
  added for retrieving XFLT keywords from data files.

- Norm parameters are now set with a default 'soft' upper limit below
  their 'hard' upper limit.

- In PyXspec, the Fit.statMethod and statTest attributes can now be set
  for individual spectra.

Enhancements previously released as patches to 12.8.0:

- AtomDB has been upgraded to version 2.0.2.

- The tclout 'stat' and 'statmethod' options can now retrieve the test
  statistic as well as the fit statistic.

- The simftest Tcl script command now takes an optional filename
  argument for output.

- Attributes added to PyXspec classes: Xset.parallel, Fit.statTest.

All bug fixes to v12.8.0 released as patches are included in v12.8.1.
In addition the following problems have been corrected:

- The command history file xspec.hty (in the user's ~/.xspec directory)
  is now updated when exiting XSPEC with the 'quit' command.  Previously
  it was only updated when exiting with 'exit'.

- The 'chain' command can now read/write files in ASCII format when
  running in the default Goodman-Weare mode.  Previously this feature
  was only available for Metropolis-Hastings chains.

- Fix to an array access error in the nthcomp model.

- PyXspec fix removes error messages generated when accessing response
  parameters in Python versions 2.6.x.