Binary Orbital Phase Calculation
(gtophase Tutorial)

Prerequisites

• Event data file in FT1 format a.k.a. a photon data file. (See Extract LAT Data).

• Orbit file to use for the barycentric correction

• Pulsar ephemeris database file which contains binary orbital parameters of a pulsar of interest

• Right Ascension (R.A.) and Declination (Dec) of the source (pulsar) location for the barycentric correction

Sample Files. To try the examples in this section, you can download the following fake data files:

SciTools Reference Pages: If you want the SciTools Reference pages to open in a popup window, click on: Open Popup Reference Window.

How To Assign Orbital Phases

The tool automatically extracts one or more ephemerides from an existing pulsar ephemerides database file. Unlike the similar tool gtpphase, there is no option for entering orbital ephemerides manually. This tool does not produce a separate output file, but operates directly on the input file in place. If execution is successful, the tool produces no textual output.

The following plot of the modified events file was produced by fplot, and shows the ORBITAL_PHASE column as a function of TIME in the events file.

Getting More Information on Computation

If gtophase is invoked with chatter parameter set to 4 or larger, it will display brief summaries of loaded ephemerides, arrival time corrections, and time systems being used. This feature shows you additional information on computations being performed, which may help you understand the tool. Also, the extra information printed may contain a clue to diagnose certain types of problem. So, try a high chatter when you are unsure on the tool's behavior.