Differential Frequency-dependent Delay from the Pulsar Magnetosphere
Abstract
Some radio pulsars show clear drifting subpulses, in which subpulses are seen to drift in pulse longitude in a systematic pattern. Here we examine how the drifting subpulses of PSR B0809+74 evolve with time and observing frequency. We show that the subpulse period (P3) is constant on timescales of days, months and years, and between 14-5100 MHz. Despite this, the shapes of the driftbands change radically with frequency. Previous studies have concluded that, while the subpulses appear to move through the pulse window approximately linearly at low frequencies (< 500 MHz), a discrete step of 180 degrees in subpulse phase is observed at higher frequencies (> 820 MHz) near to the peak of the average pulse profile. We use LOFAR, GMRT, GBT, WSRT and Effelsberg 100-m data to explore the frequency-dependence of this phase step. We show that the size of the subpulse phase step increases gradually, and is observable even at low frequencies. We attribute the subpulse phase step to the presence of two separate driftbands, whose relative arrival times vary with frequency - one driftband arriving 30 pulses earlier at 20 MHz than it does at 1380 MHz, whilst the other arrives simultaneously at all frequencies. The drifting pattern which is observed here cannot be explained by either the rotating carousel model or the surface oscillation model, and could provide new insight into the physical processes happening within the pulsar magnetosphere.
Cite
@article{arxiv.1302.2321,
title = {Differential Frequency-dependent Delay from the Pulsar Magnetosphere},
author = {T. E. Hassall and B. W. Stappers and P. Weltevrede and J. W. T. Hessels and A. Alexov and T. Coenen and A. Karastergiou and M. Kramer and E. F. Keane and V. I. Kondratiev and J. van Leeuwen and A. Noutsos and M. Pilia and M. Serylak and C. Sobey and K. Zagkouris and R. Fender and M. E. Bell and J. Broderick and J. Eisloffel and H. Falcke and J. -M. Griessmeier and M. Kuniyoshi and J. C. A. Miller-Jones and M. W. Wise and O. Wucknitz and P. Zarka and A. Asgekar and F. Batejat and M. J. Bentum and G. Bernardi and P. Best and A. Bonafede and F. Breitling and M. Bruggen and H. R. Butcher and B. Ciardi and F. de Gasperin and J. -P. de Reijer and S. Duscha and R. A. Fallows and C. Ferrari and W. Frieswijk and M. A. Garrett and A. W. Gunst and G. Heald and M. Hoeft and E. Juette and P. Maat and J. P. McKean and M. J. Norden and M. Pandey-Pommier and R. Pizzo and A. G. Polatidis and W. Reich and H. Rottgering and J. Sluman and Y. Tang and C. Tasse and R. Vermeulen and R. J. van Weeren and S. J. Wijnholds and S. Yatawatta},
journal= {arXiv preprint arXiv:1302.2321},
year = {2013}
}
Comments
10 pages, 6 figures, accepted for publication in Astronomy and Astrophysics