National Aeronautics and Space Administration

HEAO-1 Software

General FITS file manipulation: The FTOOLS package, futils, provides a suite of programs that can be used to view and manipulate any of the HEAO-1 FITS files. To view the data particularly useful are the tasks fplot (to plot the data), fdump (to dump the data file content), fstruct and flcol (to get the structure and column name of the FITS files). Basic selection and column manipulation can be done using fselect (to select rows based on the result of a boolean expression), fcalc (to calculate values for new column based on arithmetic expression) and fstatistic (to compute standard statistical value on a column). Alternatively most of the operations (and more) mention above can be done using fv, the interactive FITS file viewer and editor.

Spectra and Lightcurves : Spectra and lightcurves can be analyzed using Xspec and Xronos respectively. Xspec is a general spectral fitting programs, providing a number of already made standard models. To use XSPEC with the HEAO-1 A2 & A4 archive files, it is necessary to extract from the archive a source and background spectrum and a response matrix.
The HEAO-1 A1 & A2 lightcurves can be used in any of the Xronos programs, each dedicated to a specific timing task.

Note: The area in the file refer to the nominal on-axis area of the detector and the spectra have not been corrected for the reduction in the collimator efficiency during the period when the source was observed off-axis. Therefore the count rate and the normalization in the spectral fitting maybe be incorrect.

A2 Raw rates files : To extract a lightcurve or a scan profile from the HEAO-1 raw rate and scanning data, three programs are available : a2source, a2lcurve, and dsdlcurve. These programs are part of the HEAO-1 package distributed with the FTOOLS. A2source and a2lcurve operate on the A2 raw rate data and dsdlcurve operates on the DSDISK data. No software is available for the LED detectors.

• Extracting a lightcurve from the A2 Raw rates files.

  The first step in extracting a lightcurve from the raw rates files is to determine which files contain times when the HEAO-1 A2 MED and HED detectors viewed the sky position containing the source. A2source, for a given sky position, provides a listing of these files. After a file listing is available a2lcurve operates on the 5.12 sec raw rates data from either the MED or HED detectors and extracts a lightcurve. A2lcurve allows for small or large field of view lightcurves to be extracted based on the choice of "discovery scalars". An example of the use of these routines on the source SMC X-1 (coordinates R.A.(1950)=01^h 15^m 45.7^s, Dec (1950)=-73° 42' 21.8'') is given here.

• Extracting a scan profile from the A2 DSDISK files.

  Dsdlcurve uses the raw scanning data and accumulates a 25 degree scan profile in the vicinity of the source position during all times when the source was in the detector FOV. An example using dsdlcurve is given here.

A2 Raw rates Analysis Issues

• The Discovery Scalars
• The Pre-defined Weights for the Discovery Scalars
• Standard Background Correction
• History of A2 Detector