Chandra Interactive Analysis of Observations
CIAO is the software package developed by the Chandra X-Ray Center for analysing data from the Chandra X-ray Telescope. It can also be used with data from other Astronomical observatories, whether ground or space based.
Download CIAO/CALDB
Install CIAO 4.17 & CALDB 4.11.6
Read the CIAO 4.17 release notes for detailed information on this release, including How CALDB 4.11.6 Affects Your Analysis.
Does CIAO run on my operating system?
What are the requirements for running CIAO?
How do I install Python packages into CIAO?
CIAO 4.17 includes Python 3.11, whether installed using either of the ciao-install or conda installation methods.
What has changed?
Has there been a new release of CIAO, the contributed scripts, or the CALDB?
Version History: CIAO; Scripts & Modules.
CIAO 4.17 includes several important bug fixes as well as supports newer compilers and updated Off the Shelf software. This includes Sherpa improvements, containing the XSPEC 12.14.0k models, and SAOImage DS9 v8.6.
Where should I begin?
For those new to X-ray astronomy and data analysis
An X-ray Data Primer: What I Wish I Knew when Starting X-Ray Astronomy
Useful links for those people who have never used CIAO before.
Welcome to CIAO
Introduction to the
Tools & Applications
Introductory Science Threads - Beginners should start here
Download CIAO 4.17 using the ciao-install script
Download CIAO 4.17 with conda
I need help!
For anyone having trouble using CIAO or analysing Chandra data.
Frequently Asked Questions (FAQ)
Known CIAO Bugs and Tool Caveats
If the above links do not help you, then please contact the CXC Helpdesk. To help us help you, please include, where appropriate: the CIAO version (ciaover -v), operating system, screen output (in a text format where possible), and information on what you were trying to do.
Please include the actual text input and output (e.g. using copy and paste). Do not send in screen shots of the terminal window, as they make it much harder to identify and track down the problem.
I need more!
For the expert CIAO user or person who needs more detailed information.
Understanding the Chandra PSF.
Galleries (Tips & Tricks): CIAO; Sherpa.
The Chandra Instrument Calibration pages.
Citing CIAO
If you are writing a paper and would like to cite the CIAO software, we recommend the following:
CIAO: Chandra's data analysis system
(ADS
| PDF
| PS)
Fruscione et al. 2006, SPIE Proc. 6270, 62701V, D.R. Silvia
& R.E. Doxsey, eds.
\bibitem[Fruscione et al.(2006)]{2006SPIE.6270E..60F} Fruscione, A., et al.\ 2006, \procspie, 6270
The specific version of CIAO and CALDB used for the analysis
should be mentioned. The collect_chandra_dois () tool can be used to collect the information needed
by the Chandra Archive team to create a Chandra Data
Collection DOI.
Further guidelines are available from the Acknowledgment of Use of Chandra Resources.