# Contents¶

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.

# Setup¶

Set up some useful libraries.

:

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


Import relevant stingray libraries.

:

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 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.

:

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


Initialize transfer function by passing the array defined above.

:

transfer = TransferFunction(response)
transfer.data.shape

:

(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.

:

transfer.time_response()


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

:

transfer.time[1:10]

:

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.

:

transfer.energy_response()


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

:

transfer.energy[1:10]

:

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.

:

transfer.plot(response='2d') :

transfer.plot(response='time') :

transfer.plot(response='energy') By enabling save=True parameter, the plots can be also saved.

## IO¶

TransferFunction can be saved in pickle format and retrieved later.

:

transfer.write('transfer.pickle')


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

:

transfer_new = TransferFunction.read('transfer.pickle')
transfer_new.time[1:10]

:

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.

:

s_ir = simple_ir(dt=0.125, start=10, width=5, intensity=0.1)
plt.plot(s_ir)

:

[<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.

:

r_ir = relativistic_ir(dt=0.125)
plt.plot(r_ir)

:

[<matplotlib.lines.Line2D at 0x10cca92d0>] 