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
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.
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.
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 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
Note: The lightcurves and spectra produced by osopha are normalized by
a factor of in comparison to
the lightcurves extracted by osorat.
Before using Xspec to analyze the spectra the following steps must be
An example of this procedure is given here.
- Extract the source spectra
- Extract the background spectra (modifying the AREASCAL keyword)
- Use the closest response matrix (in time)
- Extracting a lightcurve from the superimposed A (superA) detector data.
There are routines available on the OSO-8 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
Also in the
OSO-8 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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Last modified: Tuesday, 21-Apr-2020 15:48:02 EDT