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Pulsar Polarization studies at Pulsar Polarization studies at

low radio frequencieslow radio frequencies

Dipanjan MitraDipanjan Mitra

Ncra, Tifr, Pune IndiaNcra, Tifr, Pune India

Collaborators: J Rankin, S Johnston, A Karasterigiou, S Kudale Y Gupta, J Gil

Thanks to GMRT / NCRA colleagues for their support during various projects

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Polarization observation at low Polarization observation at low

frequencies (GMRT)frequencies (GMRT)325 MHz 150 MHz

Mitra, Gupta, Kudale (2004)

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GMRT – Parkes, Pulsar Polarization survey:243, GMRT – Parkes, Pulsar Polarization survey:243,

325, 660, 1400, 3100 MHz325, 660, 1400, 3100 MHz

Johnston, Karasterigiou, Mitra, Gupta (2008)

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Average Polarization Properties

• Linear polarization of pulsars decreases with increasing frequency

RFM , OPM

• PA traverses often don’t agree with RVM and sometimes are frequency

dependent.

•Circular polarization is usually, higher towards the pulse centre

•Younger pulsars are more polarized than older pulsars

All these indicate that average polarization properties results from some

incoherent averaging process.

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Complication in Pulsar Complication in Pulsar

Polarization: PSR B0329+54Polarization: PSR B0329+54

Mitra, Rankin, Gupta 2007

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The kinky features are frequency

Independent, and spans a range of

90 degrees in PA

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Core Intensity dependent polarization Core Intensity dependent polarization

behaviourbehaviour

If pulsars after supernova kicks move

along the rotation axis then one can find

the X mode or O mode of emission

O mode should suffer from propagation

effects

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More examples of PA distortions

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Examples of PA distortions in single pulses

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90 deg PA SWINGS

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Highly polarized, narrow emission pulses

With sign changing circular. Single particle

Curvature radiation like emission

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Core intensity dependenceCore intensity dependence

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PA swing due to averaging

Of coherent emission

A/R causing shift in the PA

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PA below the core emission is a result of

•Incoherent addition of several smaller units of emission with OPM jumps in a given

subpulse. This result maybe confirmed by the observed 90 deg PA swings, and

sign changing circular, low subpulse polarization

•Due to height dependent emission of the core. This result arises from the earlier

Arrival of the core emission with intensity.

The smaller units of emission are highly polarized and show sign changing

Circular , just like a single particle curvature radiation.

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Partial cone pulsars

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Flared Pulses

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A/R effectA/R effect

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Episiodic illumination : There are different from flared pulses

Rankin et al 2007

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ConclusionConclusion• Probability of pulsar emission varies from almost 95% to ~3% across the

Pulse.

• The polarization properties of partial cones are just like other normal pulsars

And the conal emission seems to arise from about 300-400 km (like other

Pulsars).

Collaborators: J Rankin, S Johnston, A Karasterigiou, S Kudale Y Gupta, J Gil

Thanks to GMRT / NCRA staff for their support during various projects