Version 11.1 Changes

The following list summarizes, for reference, the major changes to XSPEC from version 11 to 11.1.

• Improvements in Data Input

  $\rightarrow$

  Spectral files can now have vector values of AREASCAL and BACKSCAL. XMM-RGS spectra have an AREASCAL for each channel. The vector BACKSCAL allows the grating spectrum to be extracted from a non-rectangular region on the detector. Since AREASCAL and BACKSCAL can be vectors, they are no longer prompted for in fakeit.

  $\rightarrow$

  The response command has been fixed so that XSPEC only reads the response(s) required instead of the responses corresponding to all data sets loaded. The response reading also makes more efficient use of memory, although it is still slow for large response files.

  $\rightarrow$

  The constraint that the background file must have the same grouping as the source has been relaxed. Unless the file is in the deprecated SF (non-FITS) format, the background file grouping does not matter since the source file grouping is automatically used.

  $\rightarrow$

  FITS NULL values are now trapped and replaced by 1.E-32, which should have no practical effect because channels with NULL values will presumably have bad quality set.

• Model Fitting

  $\rightarrow$

  The command model ? no longer removes the current model.

  $\rightarrow$

  The Cstat statistic has been extended to work in the case where a background spectrum has been read in. The mathematical basis for this is described in Arnaud, 2001, ApJ submitted.

  $\rightarrow$

  A new model type [acnmod] has been added for convolution on the model times the effective area. This is used for pile-up models in CCDs.

• Improvements in Output

  $\rightarrow$

  New options on the identify command:

  $\bullet$

  The user can now switch between line lists.

  $\bullet$

  The APEC line list has been added.

  $\bullet$

  The APEC option has additional options to specify a temperature and an emissivity limit, and uses the same APEC line list file as the apec model.

  $\bullet$

  If the command setplot wave has been issued, then the input range is specified in Angstroms, and wavelengths rather than energies are written out.

  $\rightarrow$

  The model rate has been added to the tclout rate option.

  $\rightarrow$

  The number of significant figures written out by the show pha command has been increased.

  $\rightarrow$

  The cosmo command now allows a cosmological constant to be set. This is only allowed if the Universe is flat (when an analytic expression is available for the luminosity distance).

• Plotting Improvements

  $\rightarrow$

  The setplot id command adds line IDs to the plots; the APEC line list is used and the temperature and emissivity limit can be set.

  $\rightarrow$

  The plot icount command makes an integrated counts plot, useful for spectra with very few counts.

  $\rightarrow$

  A new PLT feature has been used to slave any x-axis changes in the lower window to those in the upper for two-window plots. We have also explicitly included a rescale x command to ensure that the x-axis range corresponds to the data present. This overrides a PLT/PGPLOT feature that tends to produce lots of blank space on log axis plots which cover a small range.

• New Models

  ${\bf +}$

  xion performs reflection from an ionized disk.

  ${\bf +}$

  projct a mixing model that performs 3-D to 2-D projection for prolate ellipsoids.

  ${\bf +}$

  reflect a convolution model for reflection from a neutral medium. It subsumes the pexrav and bexrav models.

  ${\bf +}$

  lsmooth convolution model smoothes using a Lorentzian kernel.

  ${\bf +}$

  tbabs,ztbabs,tbgrain,tbvarabs The Tuebingen-Boulder Galactic absorption models provide better models for absorption due to the ISM. tbabs calculates absorption including molecular gas and dust. ztbabs is a redshifted version without the dust. tbgrain allows the atomic to molecular gas ratio and the grain parameters to be varied. tbvarabs allows all parameters including gas and dust metal abundances to be varied.

• Enhancements of Current Models

  $\rightarrow$

  apec,vapec The apec and vapec models have been sped up by a factor of 50-100. The model now uses the APEC v1.10 data files. The XSPEC_APEC environment variable has been added to enable the user to switch the input files in use.

  $\rightarrow$

  comptt The default ranges for comptt have been altered to better reflect the physical range of validity of the model.

  $\rightarrow$

  gsmooth A second parameter has been added to gsmooth to allow the width to vary with energy in different ways.

  $\rightarrow$

  redden,uvred The redden and uvred models have been changed to have unit transmission shortward of the Lyman limit. This is physically wrong but allows them to be used in concert with photoelectric absorption models.

  $\rightarrow$

  nei family The NEI models have slightly updated atomic physics. There is somewhat updated data for the Fe Kalpha line and a couple of bugs have been fixed. There are better collision strengths for He-like S, Ca, and Fe (and minor modifications for He-like ions for several other elements).