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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)

slide5

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.
slide7

The kinky features are frequency

Independent, and spans a range of

90 degrees in PA

core intensity dependent polarization behaviour

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

Core Intensity dependent polarization behaviour
slide12

Highly polarized, narrow emission pulses

With sign changing circular. Single particle

Curvature radiation like emission

slide15

PA swing due to averaging

Of coherent emission

A/R causing shift in the PA

slide16

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.
slide18

Flared Pulses

Mitra, Rankin, Sarala 2008

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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