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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