This notebook covers the basics of creating TransferFunction object, obtaining time and energy resolved responses, plotting them and using IO methods available. Finally, artificial responses are introduced which provide a way for quick testing.


Set up some useful libraries.

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import numpy as np
from matplotlib import pyplot as plt
%matplotlib inline

Import relevant stingray libraries.

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from stingray.simulator.transfer import TransferFunction
from stingray.simulator.transfer import simple_ir, relativistic_ir

Creating TransferFunction

A transfer function can be initialized by passing a 2-d array containing time across the first dimension and energy across the second. For example, if the 2-d array is defined by arr, then arr[1][5] defines a time of 5 units and energy of 1 unit.

For the purpose of this tutorial, we have stored a 2-d array in a text file named intensity.txt. The script to generate this file is explained in Data Preparation notebook.

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response = np.loadtxt('intensity.txt')

Initialize transfer function by passing the array defined above.

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transfer = TransferFunction(response)
(524, 744)

By default, time and energy spacing across both axes are set to 1. However, they can be changed by supplying additional parameters dt and de.

Obtaining Time-Resolved Response

The 2-d transfer function can be converted into a time-resolved/energy-averaged response.

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This sets time parameter which can be accessed by transfer.time

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array([ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.])

Additionally, energy interval over which to average, can be specified by specifying e0 and e1 parameters.

Obtaining Energy-Resolved Response

Energy-resolved/time-averaged response can be also be formed from 2-d transfer function.

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This sets energy parameter which can be accessed by

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array([ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.])

Plotting Responses

TransferFunction() creates plots of time-resolved, energy-resolved and 2-d responses. These plots can be saved by setting save parameter.

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By enabling save=True parameter, the plots can be also saved.


TransferFunction can be saved in pickle format and retrieved later.

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Saved files can be read using static read() method.

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transfer_new ='transfer.pickle')
array([ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.])

Artificial Responses

For quick testing, two helper impulse response models are provided.

1- Simple IR

simple_ir() allows to define an impulse response of constant height. It takes in time resolution starting time, width and intensity as arguments.

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s_ir = simple_ir(dt=0.125, start=10, width=5, intensity=0.1)
[<matplotlib.lines.Line2D at 0x112d48990>]

2- Relativistic IR

A more realistic impulse response mimicking black hole dynamics can be created using relativistic_ir(). Its arguments are: time_resolution, primary peak time, secondary peak time, end time, primary peak value, secondary peak value, rise slope and decay slope. These paramaters are set to appropriate values by default.

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r_ir = relativistic_ir(dt=0.125)
[<matplotlib.lines.Line2D at 0x10cca92d0>]