Pulse Portraiture

What?

A set of libraries and modules to measure "wideband" pulse times-of-arrival (TOAs), written in python. It uses an extension of Joe Taylor's FFTFIT algorithm (Taylor 1992) to simultaneously measure a phase (TOA) and dispersion measure (DM). It has subsequently been improved to also incoporate fitting for scattering parameters (timescale tau and index alpha) and frequency**-4 phase delays ("GM"). It is to be used with PSRCHIVE-compatible folded archives (PSRFITS format).

Why?

The motivation behind writing this software was to develop a wideband measurement routine for high-precision pulsar timing in the era of very broadband receivers and high-cadence timing observations for PTA experiments, and it makes up a chunk of Tim Pennucci's Ph.D. thesis. Algorithm development and coding help was provided by Paul Demorest and Scott Ransom.

How?

The technical description of this work and its related papers are:

• Pennucci, Demorest, & Ransom (2014), "Elementary Wideband Timing of Radio Pulsars", ApJ, 790, 93.

  NB: Equation 13 of the paper was written incorrectly: It should be the reverse:

  DM_bary = DM_topo / doppler_factor.

• Pennucci (2015), "Wideband Observations of Radio Pulsars", PhDT, UVa.

• Pennucci (2019), "Frequency-dependent Template Profiles for High-precision Pulsar Timing", ApJ, 871, 1.

• Pennucci et al. (in prep).

Requirements

• PSRCHIVE, compiled with the python-interface enabled,
• NumPy & SciPy recent versions will do,
• PyWavelets is required for wavelet smoothing / ppspline.py, and
• LMFIT is required for Gaussian portrait modelling / ppgauss.py and a few other functions.

TL;DR

• pplib contains functions and classes needed for the fitting scripts.
• ppspline is a command-line utility to build smoothly varying model portraits based on PCA decomposition, wavelet smoothing, and B-splin einterpolation between the components.
• ppgauss is a command-line utility to build Gaussian-component model portraits.
• pptoaslib contains functions needed for pptoas.
• pptoas is a command-line utility to measure TOAs, DMs, nu**-4 delays, and scattering parameters.
• ppalign is a command-line utility to average homogeneous data by measuring phases and DMs.
• ppzap is a command-line utility which uses pptoas to identify potentially overlooked bad channels to zap.
• The command-line programs can be imported into ipython for additional flexibility of use.
• See the examples directory for simple command-line use.
• Run and examine examples/example.py for a more in-depth demonstration.
• Try the notebook example_make_model_and_TOAs.ipynb for a walk-through.

License

Released under GPLv2, sans "or later" clause.

Other

Code improvements are underway, as is a broad application to IPTA pulsars of interest. Suggestions and additional development are welcome.