A Search for Giant Pulses from Millisecond Pulsars

We have searched for microsecond-timescale broadband emission from a sample of eighteen millisecond pulsars. Our study places strong limits on such emission from several millisecond pulsars and shows that it is only present in a small subset of millisecond pulsars. Giant pulses of up to 64 times the mean pulse energy were detected from PSR J1823−3021A in the globular cluster NGC 6624. In contrast to the giant pulses of PSR B1937+21, nearly all of the giant pulses from PSR J1823−3021A were distributed within the trailing half of the mainpulse component of the integrated pulse profile. The fact that no giant pulses were observed on the leading side of the main-pulse component suggests that giant pulses are preferentially emitted closer to the last open field line than ordinary emission. The correlation between giant pulse emissivity and spin-down luminosity in millisecond pulsars suggests that the high period derivative of PSR J1823−3021A is intrinsic and is not just an artifact of its acceleration in the gravitational potential of NGC 6624. Subject headings: pulsars:general — pulsars:individual(PSR J1823−3021A) Affiliated with the Australia Telescope National Facility, CSIRO