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Last modified: 16 December 2020


CIAO 4.13 Release Notes

CIAO 4.13 is distributed for the following platforms:

Visit our platform support page for our statement about support for macOSX 11: Big Sur .

CIAO is available using the conda package manager: conda builds are available for Linux and Mac for Python 3.8, 3.7, and 3.6. More information can be found in the conda section of the Installation notes below.

There is no support for 32 bit operating systems, older Linux (CentOS 6 era) or older macOS platforms (macOSX Sierra and earlier). More details can be found on the Platform Support page.

Notable changes and improvements in CIAO 4.13

  • CIAO 4.13 is primarily a bug fix release and includes updates to support newer compilers. There have been several enhancements to sherpa and CIAO 4.13 also provides updates to Off The Shelf (OTS) packages like SAOImage DS9.

  • CIAO can be installed using the conda package manager. Users can install the conda edition with Python 3.8, 3.7, or 3.6 on Linux and Mac.

    The ciao-install script can also be used to install CIAO 4.13 without conda, now with Python 3.7.

  • Sherpa includes both the changes made in the Sherpa 4.12.1 release and Sherpa 4.12.2 releases. Notable changes include:

    • The XSPEC library has been updated to version 12.10.1s of the XSPEC Model library, from version 12.10.1n in CIAO 4.12 (so there is essentially no change).

      Users who want to use XSPEC 12.11.1 will need to build Sherpa themselves.

      The XSPEC convolution models - such as xscflux, xszashift, and xsgsmooth - can now be used in Sherpa models.

    • Jupyter notebooks

      Many of the objects created by Sherpa will now take advantage of Jupyter notebooks to display a HTML table or an actual plot. As an example, load a PHA file with load_pha and then call get_data, or call get_source to display a model.

      jupyter notebook w/ sherpa

    • Documentation

      The Sherpa ahelp files have been updated to match the Python docstrings. Each command now has its own ahelp file, rather than combining multiple commands into a single file.

    • Multiprocessing, Python 3.8, and macOS

    • Plotting improvements

    • Flux calculations

    • PHA data handling

    As a reminder, Sherpa is also available as a stand alone system, accessible from the Sherpa GitHub repository or from the standalone Sherpa page.

  • CIAO includes version 8.2 of SAOImage ds9. Users are reminded that they now need to change the Edit mode setting in order to select or create regions in recent versions of ds9. Please see the watchout page for more information on this.

    SAOImageDS9 v8.2 highlights include:

    • Support ttk themes including Dark Mode.

      ds9 themese

    • Plot improvements, including new plot control panel

      ds9 plotting

    • Support for the Chandra and the HST footprint servers

      ds9 footprints

    • ds9 now provides a data exploration tool called Prism which has much of the same functionality as the CIAO application prism.

      ds9 data explorer

      The CIAO prism application is expected to be withdrawn in the future.

  • Several tools have been updated including

    • Updates to dmcoords allows for conversion to/from Chandra grating coordinates.

      unix% dmcoords acisf14661_001N002_evt1.fits.gz op=sky x=3731.30 y=5039.07 \
            grating=meg order=1 energy="" ra_zo=257.28179 dec_zo=-36.40712 \
            celfmt=deg verb=1
            (RA,Dec):    17:09:23.441     -36:16:48.53   
            (RA,Dec):       257.34767     -36.28015 deg
            THETA,PHI          8.289'          3.83 deg
            (Logical):        3731.30       5039.07
            SKY(X,Y):         3731.30       5039.07
            DETX,DETY         5105.09       4163.99
            CHIP ACIS-S4       152.00        223.00
            TDET              5111.00       1925.00
            GDPX,GDPY        36463.00      17042.80
            GAC R,D          0.158042    -0.0281604 deg
            ENERGY           1.123178 keV
            ZO(RA,Dec):  17:09:07.629     -36:24:25.63   
            ZO(RA,Dec):     257.28179     -36.40712 deg
            ZO SKY(X,Y):      4119.87       4110.12
            ZO DETX,DETY      4102.53       4070.14
    • Updates to wcs_update allows users to interactively select sources to use for astrometric corrections.

      unix% wcs_match 18898.dat 20056.dat out=mytransform.fits wcs=acisf20056_repro_evt2.fits \
              select=manual clob+ method=trans
      Source Residuals
      Src  Ref#  Dup#    Ref RA      Ref Dec.    Prior Resid           Transfm Resid         Resid  Incl
      Indx               (deg.)      (deg.)      RSS (x,y)             RSS (x,y)             Ratio
                                                (arcsec)              (arcsec)
       0    0     0    186.71376   -33.27030    0.57 ( 0.27, 0.51)    0.57 ( 0.27, 0.51)    0.58    Y
      Source Residual Ratios, before/after transform, and percentage improvement:
       Average Residual Ratios:   0.583753   0.583753    0.00%
       Maximum Residual Ratios:   0.583753   0.583753    0.00%
       RMS Ratios:                0.412775   0.412775    0.00%
      Please enter the Src Indx number of a source to delete (or add back), or a comma separated
      list of Src Indx numbers to delete (or add back).  Enter a -1 to finish:
    • A new tool asp_offaxis_corr has been added to allow users to update their aspect solution file to apply the proper boresite corrections (DY, DZ, DTHETA), to the RA, Dec, and ROLL values. This has a negligable change to celestial coordinates of events but does affect the off-axis angles by as much as 30".

      asol dither

  • The CXC Datamodel has several updates including important bug fixes for tab separate value ASCII files such as those returned by CSC View and for accessing virtual columns (WCS values) when additional filters are applied.

    unix% dmcopy "evt.fits[energy=500:7000][cols ra,dec]" now_works.fits
  • There have been several script updates since the CIAO 4.13 release including:

    • srcflux will now compute estimates of fluxes and rates by combining results from multiple observations.

      unix% srcflux @evt.lis pos="9:42:32.2119,+12:20:51.349" psfmethod=arfcorr out=merged/out
      Summary of merged source fluxes
            Position                               0.5 - 7.0 keV                           
                                                   Value        90% Conf Interval          
      #0001|9 42 32.21 +12 20 51.3  Rate           0.00252 c/s (0.00218,0.00286)           
        NumObi=2                    Mod.Flux       2.31E-14 erg/cm2/s (2E-14,2.62E-14)     
                                    Unabs Mod.Flux 2.44E-14 erg/cm2/s (2.11E-14,2.76E-14)  

      The new thread: Calculate source count rates and fluxes for combined datasets, shows some examples of how to do this.

    • regphystocel can be used to convert regions stored in physical coordinates (including FITS region files), into ds9 style region files in celestial coordinates.

    • There was a major update to dax in the CIAO 4.12.4 contributed scripts release which includes several additional CIAO tool, improvements to fitting with sherpa including a new parameter model editor GUI.

      list of dax tasks dax spectral desktop

  • The peg and taskmonitor tools have been removed from CIAO. The Analysis Menu item in prism has also been removed.

How CALDB 4.9.4 Affects Your Analysis

CALDB 4.9.4 Release Notes (release 15 December 2020)

ACIS Imaging and Grating Data

HRC Data


Users should be aware of these installation items before installing CIAO 4.13. Additional problems which are seen less frequently are listed on the Installation & Smoke Tests bug page.

Supported Platforms

Installing with the conda package manager

Updates to the ciao-install Installation Script

Source builds

IPython Settings

Remove old parameter files
























Parameter Files

This section provides a summary of the changes to parameter files in this release. Refer to the Tools and Analysis Scripts sections of these release notes for complete details.

We recommend deleting all the old parameter files or renaming the parameter-file directory before running any new version of CIAO to avoid conflicts. More information is available in the FAQ.





Sherpa is developed as a community project, and is available on GitHub. Comments, fixes, and additions from the community are welcomed. There are additional releases for this version throughout the year, and can be installed either directly from GitHub or using the conda package manager, as described on the standalone Sherpa documentation page.

Switching to Matplotlib

Changes to the Sherpa configuration file

Multiprocessing, Python 3.8, and macOS

Plotting improvements

Flux calculations


PHA data handling

Notable changes

Bug fixes

Graphical User Interfaces

The peg and taskmonitor tools have been removed, and the Analysis Menu in prism has been withdrawn from CIAO.



Analysis Scripts

There have been several updates to the contributed scripts package since CIAO 4.12 was released. These changes are specific to the CIAO 4.13.0 contributed scripts release.















Python Modules












Off-the-Shelf (OTS) Package Versions

Compiler versions


Many pages have been updated to reflect the changes in this release. Several analysis threads are still under review.


The CXC has decided to dropped support for ChIPS and move to using Matplotlib, alongside DS9, as the primary plotting and visualization systems in CIAO.

A ChIPS to Matplotlib conversion guide is provided for users who would like to transition from ChIPS to Matplotlib. Please contact the CXC Helpdesk if you have further questions or encounter problems.

The version of Matplotlib and choice of backend (the library that provides the visualization and any interactive capabilities) depends on how CIAO was installed.