Use of the Pulsar Timing Programs


Reading TOAs

The program psrtime takes site arrival times in a variety of formats and converts them to arrival times at the barycentre (bats), where they can then be compared with a model of the pulsar timing parameters. Many quantities in the model can be fitted to the residuals and information can then be written out in a variety of formats.

The most common form of input is to read tempo from <filename>, where the site arrival times have been written out by psrprof with the command write line tempo.


sats to bats

In order to carry out the conversion to the barycentre an ephemeris is required giving such quantities as position. The ephemeris files are in the format xxx.eph and can be written out by psrtime, containing those parameters used in the last fit to the data.

Having read in the sats, they can be sorted into chronological order and then the conversion routine called with the command jplbat. There are other conversion routines but they have been superceded.


writing bats

The program no longer requires you to define which pulsar to process, but will assume that all the data belongs to the same source (this is to allow analysis of a source under slightly different names!)

After bats have been written out for the first time together with an ephemeris file, a file is created called psrav.dat. This file contains psrtime commands and can be read back into psrtime with the obey command to set the source name ,read an ephemeris, read the bats and set the start and finish time to cover all data. The value of -1 instead of a specific date for start and finish will set those quantities to the first and last times in the data.


Using the GUI

The most used command is cursor which enables a Graphical User Interface (GUI) for displaying the residuals and fitting various quantities to the data etc. At all times the middle mouse button will show in the top right hand corner a snapshot of the pulse profile of the point nearest the position of the cursor. This is obtained from a file <file>.pro which was produced by psrprof at the same time as producing the file <file>.tpo using the command obey Also the right hand mouse button will delete the nearset point. Note that the data has not been erased, but only flagged as deleted, the button restore all bats will negate the action of those flags. If there are many points that need to be deleted then when they have been selected they can be written to a file <file>.del, which will automatically be read on and obeyed in the start up file.

The standard file name is psrav (to indicate that the data has been obtained with the averaging format in psrprof), hence there will be psrav.tpo,, psrav.eph, psrav.bat and psrav.del.


Fitting to
a model

There are many quantities that can be fitted in the model, the first set are the normal slowdown parameters, epoch, period, first and second period derivatives. A third derivative can be set but not fitted for. All these quantities can be entered as either period or frequency, the difference being in the units used, i.e. set period 30 hz is setting a frequency, but set period 0.033 secs is setting the period. Thereafter in the program both quantities are stored. The next set of quantities are dispersion measure and its time derivative ddot, ra and dec and their proper motions. There is also a full set of binary orbital parameters that can be fitted as well as exponentials. Note that although three exponentials are available only two can be fitted. Therefore the command swap exponential will swap the parameters of the given exponential with the parameters of the third exponential. In a similar manner with binary parameters, although three sets of binary parameters are available only one can be fiited, hence swap binary will swap the required set with the first set.


Other GUI

The other buttons carry out the following operations:-

  • PSR will show the pulsar parameters
  • RESI will show the residuals
  • FIT will show the latest fit
  • Fit Uaf Plot This will carry out a fit operation, then update all the parameters from the fit and then plot the new residuals.
  • Restore all Bats will remove the delete flag from all bats.
  • Load will obey a command file <file>.dat where file is the name given in the editable box immediately above the load button.
  • Restore Defaults will reset the parameters to those contained in the file <file>.eph.
  • PRSTIME Command can be used to input commands to psrtime, type the first letter and then the rest will have to be typed in the window from which psrtime was called. Return returns to the cursor screen.
  • Change parameters will show a new screen where the parameters can be altered. WARNING, this can be a source of error as the quantities shown are in internal units and maybe not in what one would expect.

The square boxes are check boxes and are set on for required operation, i.e. those quantities to be used in a fit. The round circles are radio controls and only one in a particular area can be on at any one time, in general these define what the action is when the left hand mouse button is pressed.

In general they are self explanatory, the start and finish define the time interval over which one wishes to plot or fit, rectangular delete will delete all points within an area bounded by two points. The epoch can be set at any point on the plot, this in fact does an update epoch to that date, or the button Centre can be pressed when the epoch will be set midway between the first and last data points on the screen. Bat id gives details of the nearest point to the cursor, this can be done at any time with the middle mouse button. zoom and unzoom will be centred on the point of the cursor.

Next there are some options as to how to display the data or where to send it. plot will just plot the current data, and this can be against either phase or epoch, obviously against phase has no meaning unless it is a binary pulsar. Full plot with the all data check box on will display all the data that was in the bat file, for the Crab this is a lot of points. There is also a little plot produced above the main plot which always shows all the data between start and finish when starting cursor, hence even if one zooms in and out etc, this will still show all that data, making it easier to reset start and finish outside the current plot. If the To file box is on then when hitting plot the residuals will be written to a file <file>.res, and if the hardcopy box is on then a postscript file called <file>.ps will be generated for that plot.

Remove wave is a specialised facility, used for removing long term timing noise for examination of proper motion etc.


Writing out

The last set of buttons are very important allowing transfer of data with the outside world. Having obtained the best fit to the data a new ephemeris can be written out, using the WR NewEph button, there are safeguards built in to check in case you are potentially overwriting an existing ephemeris. The other output is WRCorrect. This will output the ephemeris to a file called correct.dat, which has a format so that it can be read into psrprof to correct the data from the online ephemeris to this new one. It is suggested that as soon as this file is written it be renamed as the next file will also be called correct.dat. There are two other buttons Wr Del and Rd Del, these will write to and read from a file called <file>.del those points that have been deleted. The last button that is used is WrTempo, this will write out the fit in a format that can be read by the tempo program for producing an ephemeris for copying to the pulsar public ftp area.



May 8, 2001
Psrtime Commands
Psrtime Parameters