PSR B0809+74: Understanding its perplexing subpulse-separation (P$_\mathsf{2}$) variations

Abstract

Abstract. The longitude separation between adjacent drifting subpulses, P 2 , is roughly constant for many pulsars. It was then perplexing when pulsar B0809+74 was found to exhibit substantial variations in this measure, both with wavelength and with longitude position within the pulse window. We analyze these variations between 40 and 1400 MHz, and we show that they stem primarily from the incoherent superposition of the two orthogonal modes of polarization.

Differential frequency-dependent delay from the pulsar magnetosphere

“…Certainly, the fits to the P 3 -folded pulse stacks shown here look very similar to the islands of polarisation seen in Figs. 5 and 6 of Rankin et al (2005), although unfortunately we do not yet have polarisation data to test this hypothesis directly. In the following discussion, we attempt to reconcile our findings with models of the pulsar magnetosphere.…”

Phenomenology of pulsar B0809+74's rotating subbeam system

“…Well measured values of P 2 for B0809+74, in fact, exhibit only a slight frequency dependence as discussed in Rankin et al (2005) -indeed, one which is difficult to discern in the range between about 100 MHz and 21 cm. Note that the model P 2 in Table 2, computed using Eq.…”

“…The primary Westerbork Synthesis Radio Telescope (hereafter WSRT) observations at 1380 and 328 MHz and Pushchino Radio Astronomy Observatory (PRAO) sequences at 112.7 and 41.0 MHz used in our analyses below are identical to those studied previously (and described in detail) by Ramachandran et al (2002) and Rankin et al (2005); therefore, we here merely summarize their main properties in Table 1. In addition we will make use of a set of 328, 382, 1375, and 4880 MHz WSRT total-power average profiles to study their relative alignment.…”

“…Both the linear depolarization and slightly nonorthogonal polarization-mode mixing in this outside conal edge region of the emission beam tend to distort the overall average polarization-angle (hereafter PA) traverse (Ramachandran et al 2002;e.g., Ramachandran et al 2004, for a similar effect in B2016+28) and frustrate any ready geometrical interpretation for such stars (e.g., Lyne & Manchester 1988;Rankin 1993a,b). It has been possible to show that the complex polarization-modal structure of the drifting subpulses in B0809+74 are largely responsible for the old and perplexing reports of both longitude and frequency variations in the subpulse interval P 2 (Rankin et al 2005, hereafter RRS; see also Edwards & Stappers 2003.…”

Phenomenology of pulsar B0809+74's rotating subbeam system

“…Both the linear depolarization and slightly nonorthogonal polarizationmode mixing in this outside conal edge region of the emission beam tend to distort the overall average polarization-angle (hereafter PA) traverse and frustrate any ready geometrical interpretation for such stars (e.g., Lyne & Manchester 1988;Rankin 1993a,b). It has been possible to show that the complex polarization-modal structure of the drifting subpulses in B0809+74 are largely responsible for the old and perplexing reports of both longitude and frequency variations in the subpulse interval P 2 (Rankin et al 2005, hereafter RRS; see also Edwards & Stappers 2003, 2004.…”