Pulsar scintillation screens

Analyze and model pulsar dynamic spectra, using secondary spectra and theta-theta decompositions for linear screens.

Everything here is super-preliminary and in constant flux.

Installation instructions

The package and its dependencies can be installed with:

pip install git+https://github.com/mhvk/screens.git#egg=screens

License

This project is Copyright (c) M.H. van Kerkwijk and licensed under the terms of the GNU GPL v3+ license. This package is based upon the Astropy package template which is licensed under the BSD 3-clause licence. See the licenses folder for more information.

Background

• Simple scintillometry examples: the dynamic and secondary spectra, and wavefield for elementary situations

• Scattering by multiple linear screens: derivation of the scattering angles and velocities

• Scintillation velocities: derivation for a pulsar on a circular orbit and a single linear screen

• Glossary of symbols: list of terms used in modelling scintillation velocities

Tutorials

Generating and processing scintillometry data

• Single screen synthetic data example: how to generate the dynamic and secondary spectrum

• Different transforms for constructing secondary spectra: how the nu-t transform preserves features best in wide-band data

• Using the Screen1D class: generate synthetic data and visualize the system (for a single screen)

• Simulating a multiple-screen system: how to use Screen1D for radiation scattered by multiple screens

• Simulating VLBI Data: how to use the Screen1D class to generate VLBI data

Modelling scintillation velocities

This is a sequence of interconnected tutorials dealing with time series of scintillation velocities (or curvature). See also the background document on scintillation velocities for a derivation of the equation appearing in these tutorials.

• Generating synthetic scintillation velocities: make synthetic time series of scintillation velocities or curvature

• Fitting scintillation velocities: fit a phenomenological model to a time series of scintillation velocities

• Inferring physical parameters: retrieve the physical parameters of the system from the fit

• Error analysis: propagate uncertainties from fitting parameters to physical parameters

Reference/API

screens.screen Module

Representations for sources, screens, and telescopes.

Warning

experimental, i.e., API likely to change. For an example, see examples/two_screens.py.

Classes

Source([pos, vel, magnification])	Source of radiation at a given position and velocity.
Screen([pos, vel, magnification, source, ...])	Screen passing through a source of radiation.
Telescope([pos, vel, magnification, source, ...])	Telescope detecting a source of radiation.
Screen1D(normal[, p, v, magnification, ...])	One-dimensional screen.

Class Inheritance Diagram

screens.fields Module

Functions

phasor(indep, transform[, linear_axis])	Calculate phase part of a Fourier transform like operation.
dynamic_field(theta_par, theta_perp, ...[, fast])	Given a set of scattering points, construct the dynamic wave field.
theta_grid(d_eff, mu_eff, fobs, dtau, ...)	Make a grid of theta that sample the parabola in a particular way.
theta_theta_indices(theta[, lower, upper])	Indices to pairs of angles within bounds.

screens.dynspec Module

Classes

DynamicSpectrum(dynspec, f, t[, noise])

Dynamic spectrum and its axes.

Class Inheritance Diagram

screens.conjspec Module

Classes

ConjugateSpectrum(conjspec, tau, fd[, noise])

Conjugate spectrum and methods to fit it.

Class Inheritance Diagram

screens.remap Module

Functions

lincover(a, n)	Cover the range spanned by a in n points.
remap_time(ds, t_map, new_t)	Remap DS(t, f) to new(t_map[t], f).

screens.modeling Module

Classes to model dynamic and conjugate spectra.

This is very much work in progress, with a somewhat illogical combination of the various fitting methods in a single class.

Classes

DynamicSpectrumModel(ds[, d_eff, mu_eff, ...])	Model a dynamic spectrum.
ConjugateSpectrumModel(cs[, d_eff, mu_eff, ...])	Conjugate spectrum and methods to fit it.

Class Inheritance Diagram

screens.visualization Package

Functions

axis_extent(*args)	Treat the arguments as axis arrays of an image, and get their extent.
make_sketch(theta[, beta, screen_y_scale, ...])	Draw a schematic of the thin-screen model of for scintillation.

Classes

ThetaTheta(theta)

Class Inheritance Diagram