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Pulsar Polarization studies at low radio frequencies

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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Pulsar Polarization studies at low radio frequencies

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  1. 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

  2. Polarization observation at low frequencies (GMRT) 150 MHz 325 MHz Mitra, Gupta, Kudale (2004)

  3. GMRT – Parkes, Pulsar Polarization survey:243, 325, 660, 1400, 3100 MHz Johnston, Karasterigiou, Mitra, Gupta (2008)

  4. 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.

  5. Complication in Pulsar Polarization: PSR B0329+54 Mitra, Rankin, Gupta 2007

  6. The kinky features are frequency Independent, and spans a range of 90 degrees in PA

  7. 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

  8. More examples of PA distortions

  9. Examples of PA distortions in single pulses

  10. 90 deg PA SWINGS

  11. Highly polarized, narrow emission pulses With sign changing circular. Single particle Curvature radiation like emission

  12. Core intensity dependence

  13. PA swing due to averaging Of coherent emission A/R causing shift in the PA

  14. 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.

  15. Partial cone pulsars

  16. Flared Pulses Mitra, Rankin, Sarala 2008

  17. A/R effect

  18. Episiodic illumination : There are different from flared pulses Rankin et al 2007

  19. 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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