Abstract
Single pulses preserve information about the pulsar radio emission and propagation in the pulsar magnetosphere, and understanding the behaviour of their variability is essential for estimating the fundamental limit on the achievable pulsar timing precision. Here we report the findings of our analysis of single pulses from PSR J1713+0747 with data collected by the Large European Array for Pulsars (LEAP). We present statistical studies of the pulse properties that include distributions of their energy, phase and width. Two modes of systematic sub-pulse drifting have been detected, with a periodicity of 7 and 3 pulse periods. The two modes appear at different ranges of pulse longitude but overlap under the main peak of the integrated profile. No evidence for pulse micro-structure is seen with a time resolution down to 140 ns. In addition, we show that the fractional polarisation of single pulses increases with their pulse peak flux density. By mapping the probability density of linear polarisation position angle with pulse longitude, we reveal the existence of two orthogonal polarisation modes. Finally, we find that the resulting phase jitter of integrated profiles caused by single pulse variability can be described by a Gaussian probability distribution only when at least 100 pulses are used for integration. Pulses of different flux densities and widths contribute approximately equally to the phase jitter, and no improvement on timing precision is achieved by using a sub-set of pulses with a specific range of flux density or width.
Highlights
Millisecond pulsars (MSPs) that were spun up in accreting binary systems to reach rotational periods 30 ms (Alpar et al 1982) are noted for their highly precise timing behaviour (e.g. Arzoumanian et al 2015; Desvignes et al 2016; Reardon et al 2016)
At the Westerbork Synthesis Radio Telescope (WSRT), the PuMa-II system (Karuppusamy, Stappers & van Straten 2008) was used to record 8-bit baseband data of 8 × 20 MHz bands, with central frequencies at 1342, 1358, 1374, 1390, 1406, 1422, 1438 and 1454 MHz.2. At both Effelsberg and the WSRT, the data were later copied to discs and shipped to the Jodrell Bank Observatory (JBO), where they were installed into the Large European Array for Pulsars (LEAP) central storage cluster
The observation recorded a total of 196 915 single pulses, approximately 75 per cent of which were detected with a peak signal-to-noise ratio (S/N) higher than 5 based on a time resolution of 9 μs
Summary
Millisecond pulsars (MSPs) that were spun up in accreting binary systems to reach rotational periods 30 ms (Alpar et al 1982) are noted for their highly precise timing behaviour (e.g. Arzoumanian et al 2015; Desvignes et al 2016; Reardon et al 2016). Detailed studies of single pulse variability in MSPs are crucial for building a comprehensive understanding of this phenomenon, if we are to push beyond this limitation Such investigations will provide input for the efforts to either model or mitigate jitter noise in timing data (Osłowski et al 2011; Imgrund et al 2015). Investigations into ordinary single pulses of MSPs have been carried out only for a limited number of bright sources (Jenet et al 1998; Edwards & Stappers 2003; Bilous 2012; Shannon & Cordes 2012; Osłowski et al 2014; Shannon et al 2014; Liu et al 2015), one of which is PSR J1713+0747 This pulsar is one of the most precisely timed pulsars and has been included in current pulsar timing array campaigns to detect gravitational waves in the nanohertz frequency range (Verbiest et al 2016).
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