Determination of linear polarization and faraday rotation of pulsar signals from spectral intensity modulation |
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Authors: | P S Ramkumar A A Deshpande |
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Institution: | (1) Raman Research Institute, C.V Raman Avenue, 560 080 Bangalore, India |
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Abstract: | Most of the known pulsars are sources of highly linearly polarized radiation. Faraday rotation in the intervening medium rotates
the plane of the linear polarization as the signals propagate through the medium. The Rotation Measure (RM), which quantifies
the amount of such rotation as a function of wavelength, is useful in studying the properties of the medium and in recovering
the intrinsic polarization characteristics of the pulsar signal. Conventional methods for polarization measurements use telescopes
equipped with dual orthogonally polarized feeds that allow estimation of all 4 Stokes parameters. Some telescopes (such as
the Ooty Radio Telescope) that offer high sensitivity for pulsar observations may however be receptive to only a single linear
polarization. In such a case, the apparent spectral intensity modulation, resulting from differential Faraday rotation of
the linearly polarized signal component within the observing bandwidth, can be exploited to estimate the RM as well as to
study the linear polarization properties of the source. In this paper, we present two improved procedures by which these observables
can be estimated reliably from the intensity modulation over large bandwidths, particularly at low radio frequencies. We also
highlight some other applications where such measurements and procedures would be useful. |
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Keywords: | Stars: neutron pulsars interstellar medium: Faraday rotation telescope: polarization |
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