Pulsar Polarization studies at low radio frequencies

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Pulsar Polarization studies at low radio
frequencies

• Dipanjan Mitra
• Ncra, 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 frequencies (GMRT)
150 MHz
325 MHz
Mitra, Gupta, Kudale (2004)
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GMRT Parkes, Pulsar Polarization survey243,
325, 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 dont 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 Polarization PSR B032954
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 behaviour
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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 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
Mitra, Rankin, Sarala 2008
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A/R effect
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Episiodic illumination There are different
from flared pulses
Rankin et al 2007
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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