The most simple pulsar data format is the ephemeris. This is the parameters used in the timing model. Ephemerdies come as text files with a .eph or .par extension.
There appears to be no formal specification of what parameters are used in these files, although a loose standard has developed, with the following common parameters.
| Parameter | Units | Description | Aliases |
|---|---|---|---|
| PSRJ | String | Pulsar JName | |
| RAJ | sex-hr | Right Asscention (J2000) | |
| DECJ | sex-deg | Declination (J2000) | |
| PEPOCH | MJD | Period Epoch | |
| F0 | Hz | Fundemental frequency of the PSR | F (sometimes P/P0, the period) |
| F1 | Hz/s | First derivitive of rotational freq | |
| F2 | Hz/s/s | Second derivitive of rotational freq | |
| POSEPOCH | MJD | Position Epoch | |
| DM | pc/cm3 | Dispersion Measure | |
| START | MJD | Time the eph is valid from | |
| FINISH | MJD | Time the eph is valid till | |
| BINARY | String | The binary model used (if any) | |
| EPHVER | Integer | The eph version |
The parameters for the binary motion are dependent on the binary model used.
For the BT model:
| Parameter | Units | Description | Aliases |
|---|---|---|---|
| A1 | ltsec | projected semimajor axis | |
| ECC | Eccentricity of the orbit | E | |
| T0 | MJD | Epoch of periastron | |
| PB | days | Orbital Period | |
| OM | deg | Longitude of Periastron |
The files are tab or whitespace seperated with a single line for each keyword. Note that exponentials can be writen with a standard ‘e’ notation, or the rather more strange ‘D’ notation. e.g.
PSRJ 1722–2210 F0 1.23234234 F1 2.34567D-02
The files produced by tempo and psrtime should be compatable. tempo2 can read tempo files, with the -tempo1 switch. tempo2 files are not backwards compatible to psrtime.
Catagories: Data Formats