Subpulse drifting, nulling, and mode changing in PSR J2006 − 0807 with core emission

Abstract

We report a detailed analysis of the emission behaviour of the five component, core-double cone, pulsar J2006−0807 (B2003−08). The single pulses revealed the presence of the three major phenomena of subpulse drifting, nulling and mode changing. The pulsar switched between four different emission modes, two of which showed systematic drifting with prominent drift bands, and were classified as modes A and B respectively. The drifting was seen primarily in the conal components and exhibited the rare phenomenon of bi-drifting, where the drift direction in the second component was opposite to the fourth component. This made PSR J2006−0807 the only known example where systematic drift bands were seen around a central core emission. The emission showed a gradual decrease in intensity during mode A which stabilised to a relatively constant level in the subsequent mode B. The presence of a low frequency, weak and wide structure in the fluctuation spectra was also seen primarily in the core component during modes A and B. The core component vanished during mode C and was most prominent during the fourth mode D. Both these modes were frequently interspersed with null pulses. No detectable drifting was seen during modes C and D, but the pulsar showed short duration periodic nulling in the core as well as the conal components. In addition to the four emission modes the pulsar also nulled for long durations lasting up to hundred rotation periods.

Periodic Modulation: Newly Emergent Emission Behavior in Pulsars

“…Detailed work of Herfindal & Rankin (2009) identified additional 9 pulsars to show this behaviour, which was further increased to a total of 19 pulsars by Basu et al (2017, see Table 3 of this paper). Subsequently, pe- riodic nulling was also detected in PSR B0823+26 (Basu & Mitra 2019), PSR B1819−22 (Basu & Mitra 2018b) and PSR B2003−08 (Basu et al 2019b). We have identified an additional 8 pulsars which exhibit periodic nulling in Table 1.…”

“…Subpulse drifting is seen only in conal pairs, where the outer pairs have phase stationary behaviour and the inner pairs exhibit large scale bidrifting behaviour. Periodic nulling is seen across entire profile as a phase stationary behaviour (Basu et al 2019b). Another pulsar B1737+13, with M type profile, shows presence of both subpulse drifting and periodic amplitude modulation.…”

Radio emission features in different modes of PSR J0826+2637 (B0823+26)

“…Figure 1 (right panel) shows the presence of nulling during the Q-mode, while figure 4 shows examples of short nulls during B-mode. We have carried out a detailed analysis of nulling using the techniques described in Basu et al (2017); Basu & Mitra (2018b); Basu et al (2019b). This included estimating the energy distributions for the on and off-pulse windows to determine the nulling fractions as well as the distribution for consecutive null and burst pulses (Ritchings 1976).…”

Periodic mode changing in PSR J1048−5832

“…The fractional circular polarization in the weak mode is relatively high with a sense reversal between the leading and central components. Both the PA swing and the overall pulse width are identical for the two modes and such behavior has also been seen in PSRs J1822−2256 (Basu & Mitra 2018) and J2006−0807 (Basu et al 2019b), which suggests that the emission of the two modes comes from the same general emission region. Additionally, we compare total intensity of the two modes in Fig.…”

“…Periodic nulling has been reported in some pulsars (Herfindal & Rankin 2007, 2009Rankin & Wright 2008;Rankin et al 2013;Gajjar et al 2014Gajjar et al , 2017Basu et al 2017;Basu & Mitra 2018;Basu et al 2019b;Basu & Mitra 2019). Observed periodicities in the amplitude modulation of some components of some pulsars are very similar to periodic nulling, and therefore Basu et al (2017) suggested that they have a common origin.…”