2020MNRAS.499..906B

We have carried out a detailed study of single pulse emission from the pulsar B2000+40 (J2002+4050), observed at 1.6-GHz frequencies using the Effelsberg radio telescope. The pulsar has three components, which are not well separated, with the central component resembling core emission. We have investigated modulations in single pulse behaviour using the fluctuation spectral analysis, which showed the presence of two prominent periodicities, around 2.5P and 40P, respectively. The shorter periodicity was associated with the phenomenon of subpulse drifting and was seen to be absent in the central core component. Drifting showed large phase variations in conal components. Additionally, the periodic modulations had significant evolution with time, varying between very sharp and highly diffuse features. In addition to drifting the pulsar also had the presence of nulling in the single pulse sequence. The longer periodic feature in the fluctuation spectra was associated with nulling behaviour. The pulsar joins a select group, which shows the presence of the phase-modulated drifting as well as periodic nulling in the presence of core emission. This provides further evidence for the two phenomena to be distinct from each other with different physical origins.