Ephemeris Data File (gtpulsardb) Tutorial
The gtpulsardb tool is a utility for manipulating and accessing databases containing pulsar ephemeris data. Using this tool, one can accept input from any number of FITS files in the Fermi D4 format, and/or simple text files containing pulsar data. These input pulsar ephemerides can be filtered by pulsar name and other criteria, and the results stored in a new Fermi D4 FITS file. Prerequisites
Sample FilesTo try the following examples, download fake data files from:
How to Filter an Existing Pulsar Ephemeris FileFiltering By Pulsar NameIt is possible to filter an ephemerides file to extract only ephemerides for a particular pulsar as follows: The name supplied in the example was simply "Crab", but in general the "B-name" or "J-name" may be used as well as common names such as "Crab" or "Vela". Colloquial names and B-names are looked up using the ALTERNATIVE_NAMES extension to obtain the correct J-name, which is then used to look up ephemerides in the SPIN_PARAMETERS and/or ORBITAL_PARAMETERS. Filtering by Time RangeIt is also possible to filter an ephemerides file to extract only ephemerides which are valid during some portion of a user-specified time range, as follows: How to Merge Two or More Pulsar Ephemeris FilesIn order to merge two or more ephemerides files, it is necessary to supply more than one file name through the psrdbfile parameter. This is done using the "at-file" syntax familiar to Ftools users, in which the file names are written into a text file, and that text file is supplied to gtpulsardb with a prepended at-sign (@). How to Create a New D4 FITS FilePulsar ephemerides can also be supplied to gtpulsardb using a simple text file format. Each text file contains data which correspond to one of the four extensions in a Fermi D4 FITS file. Using the same at-file syntax described in the previous example, any number of these text files can be combined into a single Fermi D4 FITS file. Going Beyond the Simple CasesThe three examples above outline the three basic functions of gtpulsardb: filtering, merging and creating brand new Fermi D4 FITS files. However, advanced users may use the tool for more complicated tasks. For example:
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