Abstract
Abstract We have investigated the mode changing properties of PSR B0329+54 using 31 epochs of simultaneous 13 cm/3 cm single-pulse observations obtained with the Shanghai Tian Ma 65 m telescope. The pulsar was found in the abnormal emission mode 17 times, accounting for ∼13% of the 41.6 hr total observation time. Single-pulse analyses indicate that mode changes took place simultaneously at 13 cm/3 cm within a few rotational periods. We detected occasional bright and narrow pulses whose peak flux densities were 10 times higher than that of the integrated profile in both bands. At 3 cm, about 0.66% and 0.27% of single pulses were bright in the normal mode and abnormal mode, respectively, but at 13 cm the occurrence rate was only about 0.007%. We divided the pulsar radiation window into three components (C1, C2, and C3) corresponding to the main peaks of the integrated profile. The bright pulses preferentially occurred at pulse phases corresponding to the peaks of C2 and C3. Fluctuation spectra showed that C2 had excess red noise in the normal mode, but broad quasi-periodic features with central frequencies around 0.12 cycles/period in the abnormal mode. At 3 cm, C3 had a stronger quasi-periodic modulation centered around 0.06 cycles/period in the abnormal mode. Although there were some asymmetries in the two-dimensional fluctuation spectra, we found no clear evidence for systematic subpulse drifting. Consistent with previous low-frequency observations, we found a very low nulling probability for B0329+54, with upper limits of 0.13% and 1.68% at 13 cm/3 cm, respectively.
Highlights
Pulsars are fast-rotating, highly magnetized neutron stars that produce lighthouse-like beams of radio emission from their magnetic poles
We found that relatively stable integrated profiles of PSR B0329+54 can be obtained by averaging about 300 adjacent pulses
It is clear that the flux density of PSR B0329+54 at 3 cm is larger in the abnormal mode than in the normal mode
Summary
Pulsars are fast-rotating, highly magnetized neutron stars that produce lighthouse-like beams of radio emission from their magnetic poles. Dozens of pulsars in subsequent years (Lyne 1971; Ferguson et al 1981; Morris et al 1981; Wright & Fowler 1981), with a continued increase in recent times (e.g., Wang et al 2007; Burke-Spolaor et al 2012). Most of these pulsars have a complex integrated profile with multiple components. Simultaneous multi-frequency single-pulse observations are the most direct way to study whether the mode changing and subpulse drifting are wide-band phenomena and to study the intrinsic relationships between mode changes and subpulse drifts. Long-term low-frequency observations indicated that this pulsar shows relatively frequent mode changes,
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