Dipanjan mitra ncra tifr pune india
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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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Pulsar Polarization studies at low radio frequencies

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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)


Pulsar polarization studies at low radio frequencies

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.


Complication in pulsar polarization psr b0329 54

Complication in Pulsar Polarization: PSR B0329+54

Mitra, Rankin, Gupta 2007


Pulsar polarization studies at low radio frequencies

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


Pulsar polarization studies at low radio frequencies

More examples of PA distortions


Pulsar polarization studies at low radio frequencies

Examples of PA distortions in single pulses


Pulsar polarization studies at low radio frequencies

90 deg PA SWINGS


Pulsar polarization studies at low radio frequencies

Highly polarized, narrow emission pulses

With sign changing circular. Single particle

Curvature radiation like emission


Core intensity dependence

Core intensity dependence


Pulsar polarization studies at low radio frequencies

PA swing due to averaging

Of coherent emission

A/R causing shift in the PA


Pulsar polarization studies at low radio frequencies

  • 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.


Pulsar polarization studies at low radio frequencies

Partial cone pulsars


Pulsar polarization studies at low radio frequencies

Flared Pulses

Mitra, Rankin, Sarala 2008


A r effect

A/R effect


Pulsar polarization studies at low radio frequencies

Episiodic illumination : There are different from flared pulses

Rankin et al 2007


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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