gtephem Help File

Computes and displays a pulsar's frequency ephemeris for a given pulsar and instant of time.

Usage: gtephem psrdbfile psrname reftime timeformat timesys

This tool: searches for pulsar ephemerides in a pulsar ephemerides database in Fermi D4 FITS format; computes a pulse frequency and its time derivatives at the given time, using the best ephemeris available; and displays the result. If the given pulsar is in a binary system and its orbital parameters are found in the pulsar ephemerides database, it accounts for binary modulation to correct time delays due to the pulsar's orbital motion.

Examples: gtephem

To find an ephemeris for a particular pulsar at a particular time, gtephem can be invoked as follows.

> gtephem psrdbfile=bogus_pulsardb.fits psrname="PSR J9999+9999" \
reftime=54870.3 timeformat=MJD timesys=TDB

If gtephem is invoked with chatter parameter set to 4 or larger, it will display spin and orbital ephemerides that are used to compute an extrapolated spin ephemeris at a particular moment in
time, together with an extrapolated ephemeris at the given time.

> gtephem psrdbfile=bogus_pulsardb.fits psrname="PSR J1834-0010" \
reftime=54369.3 timeformat=MJD timesys=TDB chatter=4

Pulsar Ephemeris Database File

A pulsar ephemeris database file is a FITS file or a text file in a Fermi-specific format, and contains a set of pulsar ephemerides to be used in a temporal analysis of Fermi data. When so specified, the pulsar analysis ScienceTools load pulsar ephemerides from pulsar ephemeris database files, and use them in their tasks. A pulsar ephemeris database file can be created, filtered, and combined by the gtpulsardb tool. Pulsar ephemerides for the Fermi LAT pulsars and timing models associated with various Fermi publications are also available on the FSSC's Gamma-ray Pulsar Timing Database page.