gtbary Help File

gtbary performs the barycenteric correction to photon arrival times in input event file(s) using a Fermi (formerly GLAST) orbit file.

Usage: gtbary evfile scfile outfile ra dec

Upon startup, the user is prompted for the:

• Input file whose times will be corrected.
• Orbit file to use for the correction.
• Output file (which may be the same as the input file).
• Right Ascension (RA) and Declination (Dec) of the source (pulsar) location from which to correct the photons.

Three additional ancillary files are needed by gtbary in order to perform the correction:

• JPLEPH.405
• leapsec.fits
• tai-utc.dat

The program looks for these files in the directory given by the TIMING_DIR environment variable. For the moment, these files are included in the data subdirectory of the timeSystem package.

In the event that an error occurs during the correction, the input file will be left in its original state, even if the correction is being performed in place. When debugging is enabled (by typing debug=yes on the command line), a temporary file containing the state of the correction when the error occurred will be left for investigative purposes. The temporary file name is identical to the output file name with an added .tmp suffix.

Example: gtbary

In the following example, gtbary processes the event file (fakepulsar_event.fits) using the spacecraft data file (simscdata_1week.fits) for a pulsar located at right ascension 111.11, declination 22.22.

> gtbary evfile=fakepulsar_event.fits scfile=simscdata_1week.fits \
outfile=fakepulsar_event_bary.fits ra=111.11 dec=22.22

When successful, gtbary creates an output file (e.g., fakepulsar_event_bary.fits) that is ready to be given to a non-Fermi temporal analysis tool designed to analyze an event list that is in the HEASARC standard temporal file format.