OSO-8 Software

artist concept of OSO-8

The analysis of the OSO-8 GCXSE data products (e.g. FITS lightcurves) can be done using the XANADU and FTOOLS suite of programs. Public domain software can be used to view GIF files (e.g. xv on UNIX or via the Netscape browser on any system). There are also tasks available to extract lightcurves and spectra from the B and C detectors raw rates and PHA data files. There are no software available at the HEASARC to analyze the OSO-8 GCXSE A detector raw data.

* General FITS file manipulation: The FTOOLS package, futils , provides a suite of programs that can be used to view and manipulate any of the OSO-8 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.

* Lightcurves : The OSO-8 lightcurves can be used in any of the Xronos programs, each dedicated to a specific timing task.

* GCXSE B and C Raw rates and PHA files : To extract a lightcurve or spectrum from the GCXSE B and C detector raw rate or raw PHA data, three programs are available : osofindfast, osorat and osopha. These programs are part of the OSO-8 package distributed with the FTOOLS. Osorat operates on the B and C raw rate data and osopha operates on the PHA data. No software is available for the A detector however.

  • Extracting a lightcurve from the B and C raw rates files.

    The first step in extracting a lightcurve from the raw rates files is to determine which files contain times when the OSO-8 B and C detectors viewed the sky position containing the source. Osofindfast, for a given sky position determines times when that position was viewed by the A, B or C detector. This script generates the list of raw rates files appropriate for this time period. Osorat operates on the raw rates data and extracts a 160 ms lightcurve. An example of the use of these routines on the source A0620 (coordinates R.A.(1950)=95.046°, Dec (1950)=-0.32°) is given here.

  • Extracting a spectrum from the B and C raw PHA files.

    Osopha uses the raw PHA files and produces a collimator-corrected lightcurve in different energy bands and a PHA spectrum (non-background subtracted; integration time of each bin is 40.96 seconds). This task reads an ASCII file containing a list of raw PHA files. An example of the use of this routine on the source A0620 is given here.

    Note: The lightcurves and spectra produced by osopha are normalized by a factor of formula 2/pi in comparison to the lightcurves extracted by osorat.

    Before using Xspec to analyze the spectra the following steps must be followed

    • Extract the source spectra
    • Extract the background spectra (modifying the AREASCAL keyword)
    • Use the closest response matrix (in time)
    An example of this procedure is given here.
* GCXSE A Raw rates files : There are no software available to extract lightcurves or spectra from the A detector raw FITS files. However routines exist that can be used with the original superimposed A raw binary data files.

  • Extracting a lightcurve from the superimposed A (superA) detector data.

    There are routines available on the OSO8 FTP area to extract lightcurves from the superA data. These routines have not been ported to UNIX and have not been written to work with FITS data files. This software may be of value to anyone wishing to write new code to extract lightcurves from these data.

  • Extracting a spectrum from the superimposed A (superA) detector data.

    Also in the OSO8 FTP area are routines to extract spectra from the superA data. These routines have not been ported to UNIX nor have they been written to work with FITS files.

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