dedispersion

7. Dedispersion

7.1 Introduction

• Pulsars produce a narrow beam of electromagnetic radiation which rotates like a lighthouse beam, so a pulse is seen as it sweeps over a radiotelescope. The signal is spread over a wide frequency range.

• If space was an empty vacuum, all the signals would travel at the same speed, but due to free electrons different frequencies travel at slightly different speeds (dispersion), this can be corrected by performing dedispersion.

7.2 Dedisperse

This method performs dedispersion on the filterbank data.

7.2.1 Parameters

Parameters	Description
Samples	Array or sequence containing the intensities to be dedispersed.
highest_x	Specifies the amount of intensities that are used for estimating the minimum pulsar intensity
max_delay	Specifies the maximum allowed amount of samples between the currently considered pulsar signal and the next pulsar signal
DM	Dispersion measure (cm-3 pc)

7.2.2 Returns

Variable	Description
Samples	Dedispersed samples

7.3 find_dm

This method finds the dispersion measure.

7.3.1 Parameters

Parameters	Description
Samples	Array or sequence containing the intensities to be dedispersed.
pulsar_intensity	Estimation of the minimum intensity for an intensity to be considered a pulsar
max_delay	Specifies the maximum allowed amount of samples between the currently considered pulsar signal and the next pulsar signal

7.3.2 Returns

Variable	Description
dm	Dispersion measure

7.4 find_line

This method will attempt to find a continuous signal starting from the sample index given in the parameters. This method will stop if there isn't an intensity found within the max_delay higher than the pulsar_intensity.

7.4.1 Parameters

Parameters	Description
Samples	Array or sequence containing the intensities to be dedispered.
start_sample_index	The index from which this method will continue to attempt and find a continuous pulsar signal
max_delay	Specifies the maximum allowed amount of samples between the currently considered pulsar signal and the next pulsar signal
pulsar_intensity	Estimation of the minimum intensity for an intensity to be considered a pulsar

7.4.2 Returns

Variable	Description
start_sample_index	The first frequency of the continuous signal found
previous_index	The last frequency of the continuous signal found

7.5 find_estimation_intensity

This method finds the average intensity for the highest x intensities. The average_intensity is considered a requirement for intensities to be considered a pulsar.

7.5.1 Parameters

Parameters	Description
Samples	Array or sequence containing the intensities to be dedispersed.
max_delay	Specifies the maximum allowed amount of samples between the currently considered pulsar signal and the next pulsar signal

7.5.2 Returns

Variable	Description
average_intensity	Estimation of the minimum intensity for an intensity to be considered a pulsar

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