<p>Pulsars and their magnetospheres are complex. At a most basic level, the usual &quot;lighthouse&quot; model might yield two pulses per period if the line of sight from Earth to the pulsar intercepts relativisic jets emanating from both magnetic polar regions. It is boosted and beamed radiation from these magnetically confined and accelerated jets sweeping across our line of sight that causes the pulses.</p>
<p>Why might the pulses be of different strength and be not evenly spaced at phase 0 and 0.5? Simply that the magnetic field geometry is not symmetric with respect to either the rotation axis or the centre of the neutron star - for instance, an off-centre magnetic dipole. This might mean the centre of one of the beams does not fully sweep across the Earth or the jets of accelerated charged particles might not be perfectly anti-aligned.</p>

CC BY-SA 4.0
2024-12-10T23:28:21.720Z
2024-12-10T23:28:21.720Z
ProfRob
<p>The plots you show are &quot;folded&quot; light curves: they assume a period (measured some other way). They represent an average of many cycles of the periodic signal. They follow the convention of plotting two cycles of the period so that you don't have to struggle to see how the left side joins the right. If they plotted a hundred cycles it would look very periodical.</p>
<p>But if you plotted the raw data, it would not look periodical, it would just look like random noise. For most pulsar observations you need a periodogram or a folded light curve to see the pulsations.</p>
<p>We don't demand that a periodic signal only have a single pulse per period. What we demand is that the pattern of pulses repeats. We call the shortest repeating pattern in a train of pulses the &quot;period&quot;.</p>
<p>It's like music with a regular rhythm. We call the basic period of the rhythm the &quot;measure&quot;. Within the measure there's a pattern of beats that repeats from measure to measure.</p>

CC BY-SA 4.0
2024-12-11T14:14:27.703Z
2024-12-11T14:14:27.703Z
John Doty
<p>I'm an amateur wikipedia-article-jumper interested in astronomy and wanted to design a little electronic board as a badge for a few similar-minded friends. I chose a few pulsars to show them on a badge using tiny LEDs which would shine and dim, as much as possible similar to real pulsars. Having a period alone was enough but I wanted to add details and make the rise and fall time quite close to real ones. I started with the well-known, resource abundant Vela and crab pulsars.</p>
<p>While just knowing the period seemed quite easy, when I checked their light curves, I got lost. For example on the <a href="https://en.wikipedia.org/wiki/Vela_Pulsar" rel="nofollow noreferrer">Vela pulsar</a> page I found this:
<a href="https://i.sstatic.net/8MzyFK3T.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/8MzyFK3T.png" alt="Light curve for Vela pulsar" /></a></p>
<p>Which has 2 optical peaks in a period and the Gamma ray flux curve also has some peaks which don't seem very periodical to me.</p>
<p>And then for the <a href="https://en.wikipedia.org/wiki/Crab_Pulsar" rel="nofollow noreferrer">Crab pulsar</a>, I found this:
<a href="https://i.sstatic.net/C0Kef6rk.gif" rel="nofollow noreferrer"><img src="https://i.sstatic.net/C0Kef6rk.gif" alt="Crab pulsar light curve" /></a></p>
<p>Is it 2 pulses, or the pulses can be defined from 2 or more peaks? if it's 2 pulses, they why they differ greatly in brightness?</p>
<p><em>Apologies for my basic understanding.</em></p>

CC BY-SA 4.0
2024-12-08T09:59:43.023Z
The gamma ray curve is significantly noisier than the optical curve, only the two large peaks in the gamma curve that line up with the optical curve are actually signal.
Topcode
<pulsar>
Understanding a pulsar's period based on optical data
Tirdad Sadri Nejad
# Understanding a pulsar's period based on optical data

(Asked by: username_0 on 2024-12-06)

I'm an amateur wikipedia-article-jumper interested in astronomy and wanted to design a little electronic board as a badge for a few similar-minded friends. I chose a few pulsars to show them on a badge using tiny LEDs which would shine and dim, as much as possible similar to real pulsars. Having a period alone was enough but I wanted to add details and make the rise and fall time quite close to real ones. I started with the well-known, resource abundant Vela and crab pulsars.

While just knowing the period seemed quite easy, when I checked their light curves, I got lost. For example on the [Vela pulsar](https://en.wikipedia.org/wiki/Vela_Pulsar) page I found this:
[![Light curve for Vela pulsar](https://i.sstatic.net/8MzyFK3T.png)](https://i.sstatic.net/8MzyFK3T.png)

Which has 2 optical peaks in a period and the Gamma ray flux curve also has some peaks which don't seem very periodical to me.

And then for the [Crab pulsar](https://en.wikipedia.org/wiki/Crab_Pulsar), I found this:
[![Crab pulsar light curve](https://i.sstatic.net/C0Kef6rk.gif)](https://i.sstatic.net/C0Kef6rk.gif)

Is it 2 pulses, or the pulses can be defined from 2 or more peaks? if it's 2 pulses, they why they differ greatly in brightness?

*Apologies for my basic understanding.*

**Tags:** pulsar
> **Comments:**
> **username_1**: The gamma ray curve is significantly noisier than the optical curve, only the two large peaks in the gamma curve that line up with the optical curve are actually signal.  

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## 2 answers

### Answer by username_2 on 2024-12-10. Score: 4

Pulsars and their magnetospheres are complex. At a most basic level, the usual "lighthouse" model might yield two pulses per period if the line of sight from Earth to the pulsar intercepts relativisic jets emanating from both magnetic polar regions. It is boosted and beamed radiation from these magnetically confined and accelerated jets sweeping across our line of sight that causes the pulses.

Why might the pulses be of different strength and be not evenly spaced at phase 0 and 0.5? Simply that the magnetic field geometry is not symmetric with respect to either the rotation axis or the centre of the neutron star - for instance, an off-centre magnetic dipole. This might mean the centre of one of the beams does not fully sweep across the Earth or the jets of accelerated charged particles might not be perfectly anti-aligned.


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### Answer by username_3 on 2024-12-11. Score: 3

The plots you show are "folded" light curves: they assume a period (measured some other way). They represent an average of many cycles of the periodic signal. They follow the convention of plotting two cycles of the period so that you don't have to struggle to see how the left side joins the right. If they plotted a hundred cycles it would look very periodical.

But if you plotted the raw data, it would not look periodical, it would just look like random noise. For most pulsar observations you need a periodogram or a folded light curve to see the pulsations.

We don't demand that a periodic signal only have a single pulse per period. What we demand is that the pattern of pulses repeats. We call the shortest repeating pattern in a train of pulses the "period".

It's like music with a regular rhythm. We call the basic period of the rhythm the "measure". Within the measure there's a pattern of beats that repeats from measure to measure.


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