Absolute polarisation position angle profiles of southern pulsars at 1.4 and 3.1 GHz
ArXiv astro-ph/0509910 (2005)
Abstract:
We present here a direct comparison of the polarisation position angle (PA) profiles of 17 pulsars, observed at 1.4 and 3.1 GHz. Absolute PAs are obtained at each frequency, permitting a measurement of the difference in the profiles. By doing this, we obtain more precise rotation measure (RM) values for some of the pulsars in the current catalogue. We find that, apart from RM corrections, there are small, pulse longitude dependent differences in PA with frequency. Such differences go beyond the interpretation of a geometrical origin. We describe in detail the PA evolution between the two frequencies and discuss possible causes, such as orthogonal and non-orthogonal polarisation modes of emission. We also use the PA and total power profiles to estimate the difference in emission height at which the two frequencies originate. In our data sample, there are changes in the relative strengths of different pulse components, especially overlapping linearly polarised components, which coincide with intrinsic changes of the PA profile, resulting in interesting PA differences between the two frequencies.Polarization profiles of southern pulsars at 3.1 GHz
Monthly Notices of the Royal Astronomical Society 359:2 (2005) 481-492
Abstract:
We present polarization profiles for 48 southern pulsars observed with the new 10-cm receiver at the Parkes telescope. We have exploited the low system temperature and high bandwidth of the receiver to obtain profiles which have good signal-to-noise for most of our sample at this relatively high frequency. Although, as expected, a number of profiles are less linearly polarized at 3.1 GHz than at lower frequencies, we identify some pulsars and particular components of profiles in other pulsars which have increased linear polarization at this frequency. We discuss the dependence of linear polarization with frequency in the context of a model in which emission consists of the superposition of two, orthogonally polarized modes. We show that a simple model, in which the orthogonal modes have different spectral indices, can explain many of the observed properties of the frequency evolution of both the linear polarization and the total power, such as the high degree of linear polarization seen at all frequencies in some high spin-down, young pulsars. Nearly all the position angle profiles show deviations from the rotating vector model; this appears to be a general feature of high-frequency polarization observations. © 2005 RAS.Polarisation profiles of southern pulsars at 3.1 GHz
ArXiv astro-ph/0502337 (2005)
Abstract:
We present polarisation profiles for 48 southern pulsars observed with the new 10-cm receiver at the Parkes telescope. We have exploited the low system temperature and high bandwidth of the receiver to obtain profiles which have good signal to noise for most of our sample at this relatively high frequency. Although, as expected, a number of profiles are less linearly polarised at 3.1 GHz than at lower frequencies, we identify some pulsars and particular components of profiles in other pulsars which have increased linear polarisation at this frequency. We discuss the dependence of linear polarisation with frequency in the context of a model in which emission consists of the superposition of two, orthogonally polarised modes. We show that a simple model, in which the orthogonal modes have different spectral indices, can explain many of the observed properties of the frequency evolution of both the linear polarisation and the total power, such as the high degree of linear polarisation seen at all frequencies in some high spin-down, young pulsars. Nearly all the position angle profiles show deviations from the rotating vector model; this appears to be a general feature of high-frequency polarisation observations.An investigation of the absolute circular polarization in radio pulsars
Monthly Notices of the Royal Astronomical Society 352:2 (2004) 689-698
Abstract:
In most pulsars, the circularly polarized component, Stokes V, is weak in the average pulse profiles. By forming the average profile of |V| from single pulses we can distinguish between pulsars where V is weak in the individual pulses and those where large V of variable handedness is observed from one pulse to the other. We show how |V| profiles depend on the signal-to-noise ratio of V in the single pulses and demonstrate that it is possible to simulate the observed, broad distributions of V by assuming a model where |V| is distributed around a mean value and the handedness of V is permitted to change randomly. The |V| enhanced profiles of 1.3 pulsars are shown, five observed at 1.41 GHz and eight observed at 4.85 GHz, to complement the set in Karastergiou et al. (2003b). It is argued that the degree of circular polarization in the single pulses is related to the orthogonal polarization mode phenomenon and not to the classification of the pulse components as cone or core.An investigation of the absolute circular polarization in radio pulsars
ArXiv astro-ph/0405145 (2004)