Polarimetry, peculiar mode and X-ray alignment of PSR B1821-24

PSR B1821-24 is a 3.05-ms isolated pulsar located in the globular cluster M28. Its large apparent rotational energy loss rate of 2.2 X 10(36) erg s(-1) led Danner et al. (1994, ApJ, 436, L153) and, more recently, Saito et al. (1997, ApJ, 477, L77) to observe and detect this pulsar as an X-ray emitting neutron star. We report here on 800-MHz observations of B1821-24 from a polarimetry program designed to explore the magnetospheric structure of millisecond pulsars. We discuss possible alignments between the radio and X-ray beam components in the context of one and two pole emission models. We also find erratic emission from one of the components of the B1821-24 profile at 1400 MHz, but not at 800 MHz, on time scales of hours and possibly days. (C) 1997 American Astronomical Society.