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Data reduction and analysis

Typically all X-ray observations are made by X-ray detectors onboard different satellites. This data is transmitted to ground station, from where it is distributed to the scientists. All astronomical data is distributed in a standard file format called FITS format. At this point the data from a given instrument contains all the possible information available from that instrument, i.e. time, energy of all X-ray photons detected during the observation and postion of the photons in case of an imaging detector. Next step is to extract only required information from these data for further analysis, i.e. to extract light curve for timing analysis or spectrum for spectral analysis. This precess, known as data reduction, is highly instrument / mission specific and requires clear understanding  of the particular instrument. Once we have a light curve, image or spectrum in a standard format we can analyse it further to extract the scientific results.

There are some software tools available to carry out the process of data reduction and analysis. Most important software for X-ray astronomy is, HEAsoft which is maintained and distributed by HEASARC (High Energy Astrophysics Science Archive Research Center), NASA. HEAsoft includes many mission specific tools for data reduction, general purpose tools for FITS file manipulation (known as FTOOLS)  and some high level, mission independent,  data analysis software packages such XSPEC for spectral, XRONOS for timing and XIMAGE for imaging analysis. It is freely available to any one interested. We shall be using HEAsoft for all our analysis.

HEASARC also maintains archive of data observed so far from past and present X-ray / Gamma-ray missions. Typically data from any mission is publicly available from HEASARC after about one year of observation date. One can download such public data via internet and get started in exciting field of high energy astrophysics.

Latest available version,  HEAsoft v5.1A, is included with this CD so that you can install it at your favourite place and start your own X-ray data analysis. It comes in both source code distribution as well as binary distributions for Linux operating system. The source distributions can be used to compile HEAsoft for any supported operating system.

  • To compile and install HEAsoft from source code, copy the file lheasoft5.1Asrc.tar.gz to desired location, unzip and untar it and follow instructions in INSTALL.SOURCE file. Be aware that compiling from source will require about 1 GB disk space.

  • To install directly from prebuilt binary distribuion, copy the files ftools5.1Alinux_pc.tar.gz and xanadu5.1Alinux_pc.tar.gz to desired location, unzip and untar them and follow instruction in INSTALL.BINARY file. Binary install will require approaximately 300 MB disk space.

  • In either case you will need to unzip and untar the file, xspec11.1.0data.tar.gz , in the same location in order to use the spectral analysis software XSPEC.

  • This latest version of HEAsoft is not yet available for Microsoft Windows, however, an older version, FTOOLS v4.2, is available for Microsoft Windows 95, 98, ME and is included with this CD. To install FTOOLS for Windows execute the file windows_complete_ftools_42.exe and follow the instructions. This wil also require about 300 MB disk space.




This workshop is being organized by Department of Astronomy & Astrophysics, Tata Institute of Fundamental Research (TIFR) and is sponsored by Indian Space Research Organization  (ISRO).