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Dipanjan Mitra Ncra, Tifr, Pune India. Pulsar Polarization studies at low radio frequencies. 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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Dipanjan mitra ncra tifr pune india

Dipanjan Mitra

Ncra, Tifr, Pune India

Pulsar Polarization studies at low radio frequencies

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

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


Polarization observation at low frequencies gmrt
Polarization observation at low frequencies (GMRT)

150 MHz

325 MHz

Mitra, Gupta, Kudale (2004)


Gmrt parkes pulsar polarization survey 243 325 660 1400 3100 mhz
GMRT – Parkes, Pulsar Polarization survey:243, 325, 660, 1400, 3100 MHz

Johnston, Karasterigiou, Mitra, Gupta (2008)


Average Polarization Properties 1400, 3100 MHz

  • 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.


Complication in pulsar polarization psr b0329 54
Complication in Pulsar Polarization: PSR B0329+54 1400, 3100 MHz

Mitra, Rankin, Gupta 2007


The kinky features are frequency 1400, 3100 MHz

Independent, and spans a range of

90 degrees in PA


Core intensity dependent polarization behaviour

If pulsars after supernova kicks move 1400, 3100 MHz

along the rotation axis then one can find

the X mode or O mode of emission

O mode should suffer from propagation

effects

Core Intensity dependent polarization behaviour




90 deg PA SWINGS 1400, 3100 MHz


Highly polarized, narrow emission pulses 1400, 3100 MHz

With sign changing circular. Single particle

Curvature radiation like emission



PA swing due to averaging 1400, 3100 MHz

Of coherent emission

A/R causing shift in the PA


  • PA below the core emission is a result of 1400, 3100 MHz

  • 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.


Partial cone pulsars 1400, 3100 MHz


Flared Pulses 1400, 3100 MHz

Mitra, Rankin, Sarala 2008


A r effect
A/R effect 1400, 3100 MHz



Conclusion

  • 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

Conclusion


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