filtools.inject_pulsar package¶

This package contains classes designed to aid injection of pulsar and other similar signals into filterbank data

Submodules¶

filtools.inject_pulsar.ism_models module¶

class filtools.inject_pulsar.ism_models.simple_propagation_model(freq, input, dm, intra_chan=True, dm_const=0.000241)[source]¶

Bases: object

Models simple cold-plasma dispersion delays.

Optionally includes smearing due to intra-channel delay. Disable to model coherent dedispersion.

The DM delay is modeled as

\[t_\mathrm{DM} = \frac{\nu^{-2}\mathrm{DM}}{k_\mathrm{DM}}\]

Parameters:	freq – array of centre frequency for each channel in MHz. The algorithm assumes equally spaced channels. input – Callable or function. dm – the simulated DM in cm$^-3$pc. intra_chan – if True, will model the smearing in the pulse due to the intra-channel delays dm_const – override to change the DM constant ($k_\mathrm{DM}$) used to compute the DM delays.

__call__(t1, t2, mjdref)[source]¶

Compute average flux density between t1 and t2 in each frequency channel.

Output is in flux density units.

Parameters:	t1 – Start time in seconds, relative to mjdref t2 – End time in seconds, relative to mjdref
Returns:	Average flux density between t1 and t2.

class filtools.inject_pulsar.ism_models.simple_scattering_model(freq, input, t_scatt, dx, scatt_idx=-4.0, ref_freq=1400.0)[source]¶

Bases: object

Approximates thin-screen scattering in the ionised interstellar medium.

Effectively convolves the incoming signal with an exponential of the form

\[\exp{\left(-\frac{t}{t_\mathrm{scatt}}\left(\frac{\nu_\mathrm{ref}}{\nu}\right)^\alpha\right)}\]

Warning

The simple scattering model assumes that each sample to be generated is called in sequence. I.e. no calls to get_spectrum occur out of sequence. This will prevent multi-threaded operation of codes using this module.

Parameters:	input – the input signal generator freq – array of frequency channels in MHz. t_scatt – the scattering timescale. dx – the sampling interval in the data file. scatt_idx – the spectral index of the scattering timescale ($\alpha$)

__call__(t1, t2, mjdref)[source]¶

Compute average flux density between t1 and t2 in each frequency channel.

Output is in flux density units.

Warning

The simple scattering model assumes that each sample to be generated is called in sequence. I.e. no calls to get_spectrum occur out of sequence. This will prevent multi-threaded operation of codes using this module.

Parameters:	t1 – Start time in seconds, relative to mjdref t2 – End time in seconds, relative to mjdref
Returns:	Average flux density between t1 and t2.

filtools.inject_pulsar.phase_models module¶

class filtools.inject_pulsar.phase_models.precision_predictor_phase_model(predictor)[source]¶

Bases: object

A phase model that uses a phase predictor (or polyco) from tempo or tempo2. It uses the t2pred library to convert between time and phase, so can model a wide range of pulsar behaviour. This model calls t2pred on every request so is slow, but very accurate.

Parameters:	predictor (A t2pred.phase_predictor object) – The phase predictor to use

Note

This module will only function if you have installed the t2pred python library in tempo2. This can be installed using setup.py in the python/t2pred directory in the tempo2 source code.

get_frequency(time, mjdref)[source]¶: Get the pulse frequency at time in seconds relative to refmjd

get_phase(time, mjdref)[source]¶: Get the pulse phase at time in seconds relative to refmjd

class filtools.inject_pulsar.phase_models.predictor_phase_model(predictor, dt=0.1)[source]¶

Bases: object

A phase model that uses a phase predictor (or polyco) from tempo or tempo2. It uses the t2pred library to convert between time and phase, so can model a wide range of pulsar behaviour. This version keeps its own polynomial interpolation of the predictor over short spans to reduce the number of calls to t2pred and greatly increase the performance for a very minor precision reduction.

Parameters:	predictor (t2pred.phase_predictor) – The phase predictor to use dt – The interpolation window size in seconds

Note

This module will only function if you have installed the t2pred python library in tempo2. This can be installed using setup.py in the python/t2pred directory in the tempo2 source code.

get_frequency(time, mjdref)[source]¶: Get the pulse frequency at time in seconds relative to refmjd

get_phase(time, mjdref)[source]¶: Get the pulse phase at time in seconds relative to refmjd.

make_poly(t)[source]¶: This routine is used internally to make the polynomial approimation of the timing model. If a new-ish version of scipy is installed it uses scipy.interp.CubicHermiteSpline, or otherwise uses a scipy.interp.BPoly.

class filtools.inject_pulsar.phase_models.simple_phase_model(epoch, f0, f1=0.0, f2=0.0, accn=None)[source]¶

Bases: object

A very simple model of the rotational phase of a pulsar

This model is that the pulsar is in the rest frame of the observer and follows a polynomial spin where the phase is given by:

\[\phi(t) = f_0*t + (f_1*t^2)/2.0 + (f_2*t^3)/6.0$\]

phase is therefore defined as being from 0 to 1, rather than as an angle.

Parameters:	epoch – The reference epoch ($t=0$) f0 – Frequency at t=0 f1 – Frequency derivative at t=0 f2 – Frequency second derivative at t=0 accn – Doppler acceleration at t=0 (overrides choice of f1).

get_frequency(time, mjdref)[source]¶: Get the pulse frequency at time in seconds relative to refmjd

get_phase(time, mjdref)[source]¶: Get the pulse phase at time in seconds relative to refmjd

filtools.inject_pulsar.pulse_models module¶

class filtools.inject_pulsar.pulse_models.delta_pulse_model(phase_model, freq)[source]¶

Bases: object

Models a pulsar as a delta function.

Only has flux at phase zero. Phase average flux density is 1 unit.

Parameters:	phase_model – Object that implements the get_phase method. freq – An array of observing frequnecies (ignored)

__call__(t1, t2, mjdref)[source]¶

Compute average flux density between t1 and t2 in each frequency channel.

Output is in flux density units.

Parameters:	t1 – Start time in seconds, relative to mjdref t2 – End time in seconds, relative to mjdref
Returns:	Average flux density between t1 and t2.

class filtools.inject_pulsar.pulse_models.piecewise_pulse_model(phase_model, freq, profile)[source]¶

Bases: object

Models a pulsar as an arbitrary piecewise pulse shape

Parameters:	phase_model – Object that implements the get_phase method. freq – An array of observing frequnecies (ignored) profile – An array of pulse intensity as a function of time

__call__(t1, t2, mjdref)[source]¶

Compute average flux density between t1 and t2 in each frequency channel.

Output is in flux density units.

Parameters:	t1 – Start time in seconds, relative to mjdref t2 – End time in seconds, relative to mjdref
Returns:	Average flux density between t1 and t2.

repad(n)[source]¶

Pads the internal array with multiple copies of the pulse profile. Used internally to ensure that the integration can cope with profiles spanning multiple pulse periods.

Parameters:	n – The number of times to pad the profile.

class filtools.inject_pulsar.pulse_models.sinusoid_pulse_model(phase_model, freq)[source]¶

Bases: object

Models a pulsar as a sinusoid function.

\[I(\phi) = \cos{(2\pi\phi)+1}\]

Where $\phi$ is the phase in turns (i.e. between 0 and 1).

Parameters:	phase_model – Object that implements the get_phase method. freq – An array of observing frequnecies (ignored)

__call__(t1, t2, mjdref)[source]¶

Compute average flux density between t1 and t2 in each frequency channel.

Output is in flux density units.

Parameters:	t1 – Start time in seconds, relative to mjdref t2 – End time in seconds, relative to mjdref
Returns:	Average flux density between t1 and t2.