Science Using Single-Pulse Exploration with Combined Telescopes

Context. Radio pulsars exhibit a plethora of complex phenomena at the single-pulse level. However, the intricacies of their radio emission remain poorly understood. Aims. We aim to elucidate the pulsar radio emission by studying several single-pulse phenomena, how they relate, and how they evolve with observing frequency. We intend to inspire models for the pulsar radio emission and fast radio bursts. Methods. We set up an observing programme called the SUSPECT project running at the Nançay Radio Observatory telescopes in France (10–85 MHz, 110–240 MHz, and 1.1–3.5 GHz) and the upgraded Giant Metrewave Radio Telescope (uGMRT) in India. This first paper focuses on high sensitivity data of PSR B1822−09 obtained with the uGMRT between 550 and 750 MHz. The pulsar has precursor (PC), main pulse (MP), and interpulse (IP) emission and exhibits mode switching. We present its single-pulse stacks, investigate its mode switching using a hidden Markov switching model, and analyse its single-pulse morphology. Results. PSR B1822−09’s pulse profile decomposes into seven components. We show that its mode switching is well described using a hidden Markov switching model operating on single-pulse profile features. The pulsar exhibits at least three stable emission modes, one of which is a newly discovered bright flaring Bf-mode. We confirm that the PC and MP switch synchronously to each other and both asynchronously to the IP, indicating information transfer between the polar caps. Additionally, we performed a fluctuation spectral analysis and discovered three fluctuation features in its quiescent Q-mode emission, one of which is well known. We conclude that the latter feature is due to longitude-stationary amplitude modulation. Finally, we visually classified the single pulses into four categories. We found extensive microstructure in the PC with a typical duration of 0.2–0.4 ms and a quasi-periodicity of 0.8 ms. There is clear evidence of mode mixing. We discovered low-intensity square-like pulses and extremely bright pulses in the MP, which suggest bursting. Conclusions. PSR B1822−09’s PC resembles magnetar radio emission, while its MP and IP are canonical radio pulsar-like. Hence, the pulsar combines both attributes, which is rare. This work introduces several new data analysis techniques to pulsar astrophysics.