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Last modified: 19 January 2024

Science Threads

All threads

A list of all the threads on one page.

Introduction [Updated]

Beginners should start here. The Introductory threads provide an overview of the main components (GUI applications, parameter files) and concepts (the Data Model, filtering) in the CIAO data analysis software.

Data Preparation

When Chandra data goes through Standard Data Processing (SDP), the most recently available calibration is applied to it. Since this calibration is continuously being improved, one should check whether there are newer files available. Similarly, some science decisions are made during SDP; every user has the option to reprocess the data with different parameters.

Imaging [New]

The Imaging threads cover a wide range of topics that include source detection, creating exposure maps and normalized images, and calculating image statistics. How to create color images for publication is addressed, as well as merging data from multiple observations.

Imaging Spectroscopy

After extracting source and background PI or PHA spectra from an imaging observation, the appropriate response files (ARF, RMF) are created so that the data may be modeled and fit. In the case of multiple or extended sources, a weighted ARF and RMF are built for the spectral analysis.

Grating Spectroscopy

If new calibration has been applied to the event file, the grating spectrum should be re-extracted as well. It is then possible to build grating response files (gARF, gRMF) in order to model and fit the data.

Timing Analysis

In order to perform absolute timing analysis on a dataset, a barycenter correction must first be applied to the data. One may then create lightcurves and phase-binned spectra to look for variability in the source. These threads also provide information on working with data taken in the ACIS continuous clocking (CC) mode. These same tools and threads work equally well with 0th order grating data.

PSF Simulations

ChaRT is easily run with a few input parameters, producing output data files that contain the simulated HRMA PSF. The following threads illustrate collecting the necessary input for ChaRT, unpacking and identifying the output files and the final step of projecting the HRMA PSF onto the detector-plane.

Tips, Tricks, and Techniques

Most of the analysis threads are focused on a particular science goal or objective : instrument, grating, point source vs. extended, etc. They present the best path to reduce the data for those specific criteria. However, there are many kinds of analysis techniques that apply to general data reduction that can be performed with CIAO -- on Chandra data or other missions. There are far too many to have individual threads for all possible scenarios.

The threads presented in this section will focus on how to accomplish a particular task and the options available. When one should use these technique and why one would want to do such a thing are up to the user. The emphasis here is to highlight the functionality available. It is expected users will find uses for CIAO that the CXC might not have anticipated.