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# Chapter 4: Observation files

These observation files are also known as "arrival time files" or "tim files". For each pulsar an arrival time file must be created that contains all the measured site-arrival-times (i.e. the pulse arrival time at the observatory for each observation). This file can take the form of the old Parkes or Jodrell style tempo files, but it is recommended that the new tempo2 format be used. The "pat" program in the psrchive suite of software can provide arrival times in tempo2 format. A script is also available (Author: I. Stairs; click here) to convert old style files into the tempo2 format.

## 4.1: tempo2 format

The current tempo2 format is identified using

FORMAT 1

at the start of the observation file. Each line in this file can be entered in a "free-format" manner: there is no limit on the number of decimal places or characters supplied for each parameter. However, it is advisable not to use dashes (-) within the filenames, as this may confuse tempo2's understanding of potential flags. The file has the following form

file freq sat satErr siteID <flags>

where the pre-defined flags are listed in Table 4.1. Other user defined flags may be used in this file. (Do take care, however, to separate flags with spaces rather than tabs.) These flags can provide any information and could be used, for example, in determining colours used for plotting with a personal graphical interface. An example file is given below:

FORMAT 1
C ../archives/w040205_062810.cFTp 3072.52800000 53040.27037033597299853 10.07000 7 -i WBC_10
../archives/w040206_070831.cFTp 3092.99900000 53041.31851839551620031 1.16000 7 -i WBC_10
C ../archives/w040206_084839.cFTp 3068.03800000 53041.38807867413299846 9.97000 7 -i WBC_10
../archives/w040206_111139.cFTp 3105.49900000 53041.47201962440929890 1.15000 7 -i WBC_10
../archives/w040207_070619.cFTp 3092.99900000 53042.30720476755460169 1.21000 7 -i WBC_10
../archives/w040207_081328.cFTp 1367.99900000 53042.35109949197099866 1.09000 7 -i WBC_20
../archives/w040207_084227.cFTp 1415.14600000 53042.36843163794929978 0.98000 7 -i WBC_20
../archives/w040207_115804.cFTp 1431.21700000 53042.50986685147659827 0.98000 7 -i WBC_20
../archives/w040207_142934.cFTp 1431.43500000 53042.60951958276880092 0.99000 7 -i WBC_20
../archives/w040208_081840.cFTp 1563.91900000 53043.34710640092290035 0.82000 7 -i WBC_20
../archives/w040208_083501.cFTp 1432.49900000 53043.36886551809849877 0.78000 7 -i WBC_20
../archives/n2004-06-27-04:13:58.FTp 685.24900000 53183.18848980008860039 0.06000 7 -i nCPSR2_50
../archives/n2004-07-15-18:33:23.FTp 685.24900000 53201.79496983790510001 0.08000 7 -i nCPSR2_50
../archives/n2004-07-15-19:39:47.FTp 685.24900000 53201.81959222764389850 0.22000 7 -i nCPSR2_50
../archives/n2004-07-15-19:42:31.FTp 685.24800000 53201.84208218378509869 0.19000 7 -i nCPSR2_50

Table 4.1: Pre-defined flags used in arrival time files

 Flag Parameter Type dm DM (cm-3pc) float dmo DM offset (cm-3pc) float dme DM uncertainty (cm-3pc) float p Phase offset float t telescope identifier string addsat add to arrival time (seconds) float to add to arrival time (seconds) float radd add to residual (seconds?) float padd add to residual (phase) float pn pulse number (turns) int c clock correction path (underscore-separated) string telx, tely, telz telescope position (for barycentered TOAs) float

A list of the available commands that can be included in an arrival time file are provided in Table 4.2. Note that, when writing out a new arrival time file from tempo2 (using a plugin such as plk), many of these commands will not be replicated, but will instead be absorbed in the tim-file values or their errors. For example, EFLOOR, EMIN and EMAX will be absorbed in the TOA uncertainties. The exceptions are EFAC and EQUAD, which are kept separated - and hence keep the original errors intact in the tim-file. (Notice GLOBAL_EFAC and T2EFAC will be absorbed in the EFAC value and T2EQUAD will be absorbed in the EQUAD value.)

Table 4.2: Commands that may be included in an arrival time file

 Command Meaning EFAC x Multiply uncertainties by x EQUAD x Additional uncertainty in microsec, added in quadrature T2EFAC -backend dfb x Multiply uncertainties with flag "-backend dfb" by x T2EQUAD -backend dfb x Add x {$\mu$}sec uncertainty in quadrature to the errors of TOAs designated by flags "-backend dfb" GLOBAL_EFAC x Multiply all uncertainties by x. If for some or all of the TOAs an "EFAC y" is present as well, then those TOA uncertainties will multiplied by x times y. EMAX x Ignore TOAs with uncertainties greater than x (us) EMIN x Ignore TOAs with uncertainties less than x (us) EFLOOR x Put uncertainties of less than x (us) to equal x (us) END Ignore all remaining lines in the arrival time file FMAX x Ignore observations at frequencies greater than x MHz FMIN x Ignore observations at frequencies less than x MHz INCLUDE x Include the arrival times in file 'x' INFO x Identify all following observations with a given highlighting code MODE MODE 0 (default) implies that the TOA error is not taken into account during the fitting procedure. MODE 1 uses the uncertainties NOSKIP End of skip statement PHASE x Add x phase jumps SIGMA x Set uncertainties of following TOAs to x (us) SKIP Skip all lines until NOSKIP is reached TIME x Add x seconds to following TOAs TRACK x Tracks phase wrap-arounds (can also occur in parameter files)

## 4.2 The Jodrell Bank Observatory binary format

It is also possible to provide pulsar arrival times in a Jodrell Bank format binary file. Such files contain barycentric arrival times. For instance a typical usage would be

tempo2 -f psrav.eph psrav.bat -jbo -delete psrav.del