A study of multifrequency polarization pulse profiles of millisecond pulsars

Abstract

We present high signal-to-noise ratio, multi-frequency polarization pulse profiles for 24 millisecond pulsars that are being observed as part of the Parkes Pulsar Timing Array (PPTA) project. The pulsars are observed in three bands, centred close to 730, 1400 and 3100 MHz, using a dual-band 10 cm/50 cm receiver and the central beam of the 20 cm multibeam receiver. Observations spanning approximately six years have been carefully calibrated and summed to produce high S/N profiles. This allows us to study the individual profile components and in particular how they evolve with frequency. We also identify previously undetected profile features. For many pulsars we show that pulsed emission extends across almost the entire pulse profile. The pulse component widths and component separations follow a complex evolution with frequency; in some cases these parameters increase and in other cases they decrease with increasing frequency. The evolution with frequency of the polarization properties of the profile is also non-trivial. We provide evidence that the pre-and post-cursors generally have higher fractional linear polarization than the main pulse. We have obtained the spectral index and rotation measure for each pulsar by fitting across all three observing bands. For the majority of pulsars, the spectra follow a single power-law and the position angles follow a λ 2 relation, as expected. However, clear deviations are seen for some pulsars. We also present phase-resolved measurements of the spectral index, fractional linear polarization and rotation measure. All these properties are shown to vary systematically over the pulse profile.

Ion–proton pulsars: Table 1.

“…In Jones (2016) we have referred to the paper of Karastergiou & Johnston (2006) as a consequence of the number of pulsar integrated profiles observed, the signal-to-noise ration and the time resolution in that work. But the crucial feature of the circular polarization can also be seen in the papers of Han et al (1998) and of Yan et al (2011) and Dai et al (2015) on MSP. The assumptions made here are minimal.…”

TMRT Observations of 26 Pulsars at 8.6 GHz

“…Fig. 2 shows that the trailing central component 2 has a steeper spectrum than the leading component 1 and that the component separation is essentially independent of frequency (cf., Dai et al 2015). At 8.6 GHz the center components are more dominant and the side components (around 140…”

“…For most millisecond pulsars (e.g., Dai et al 2015), including PSR J0437−4715 described in §3, and some other pulsars with wide profiles, e.g., PSR J0953+0755 (B0950+08) also described in §3, the observed component separation is frequency independent. For these pulsars the emission region may be close to the light cylinder and caustic effects may be important in defining the observed profile shape (Ravi et al 2010), thereby negating the effects of radius-to-frequency mapping and providing an alternative explanation for frequency-independent component separations.…”

“…Of the 26 pulsars, 19 have two or more clearly resolved components, allowing a measurement of ∆φ as listed in Table 1. * These component separations are compared with other measurements made over a range of frequencies (Seiradakis et al 1995;von Hoensbroech & Xilouris 1997;Gould & Lyne 1998;Weisberg et al 1999;Dai et al 2015) in Fig. 4.…”

Wide-band profile domain pulsar timing analysis

“…While PSR J1909−3744 is also known to have an interpulse (eg., Dai et al 2015), as it is extremely weak we do not consider it in the profile model.…”