Detection of over 37 000 giant pulses per hour from PSR J1823−3021A with UHF baseband observations from MeerKAT

ABSTRACT Giant pulses (GPs) occur in high magnetic field millisecond pulsars and young Crab-like pulsars. Motivated by the fast radio bursts (FRBs) discovered in a globular cluster (GC) in the M81, we undertook baseband observations of PSR J1823–3021A, the most active GP emitter in a GC with the Meer Karoo Array Telescope (MeerKAT) ultra high frequency (UHF) band receiver (544–1088 MHz). The steep spectral index of the pulsar yields a GP rate of over 37 000 GPs h−1 with $\mathrm{ S/N}>7$, significantly higher than the 3000 GPs h−1 rate detected by previous work with the L-band (856–1712 MHz) receiver. Similarly to the previous work, we find that the GPs are (1) strongly clustered in two particular phases of its rotation, (2) well described by a power-law in terms of energies, (3) typically broad-band, and have steep spectral indices of ${\approx} {-}3$. Although the integrated pulse profile is not significantly polarized (${<} 1~{{\ \rm per\ cent}}$ linear and ${<} 3~{{\ \rm per\ cent}}$ circular), one of the brightest GPs displays notable polarization of 7 per cent (linear) and 8 per cent (circular). The high-time resolution data reveals the GPs have a range of single-peak and multipeak morphologies, including GPs with three distinct peaks. For the first time, we measured the temporal scattering of the pulsar using 49 bright, narrow, single-pulse GPs, obtaining a mean value of $5.5\pm 0.6$ $\mu$s at 1 GHz. The distinct periodicity and low polarization of GPs differentiate them from typical FRBs, although potential quasi-periodicity substructures in some GPs may suggest a connection to magnetars/FRBs.