Crab giant pulses at low frequencies

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, Bonn, Germany
e-mail: ramesh@mpifr-bonn.mpg.de
² Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK
e-mail: Ben.Stappers@manchester.ac.uk
³ Sterrenkunde Instituut Anton Pannenkoek, University of Amsterdam, Kruislaan 403, Amsterdam, The Netherlands
⁴ Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA, Dwingeloo, The Netherlands

Received: 8 July 2011
Accepted: 3 December 2011

Abstract

We report observations of the Crab pulsar at frequencies in the range of 110–180 MHz. The combination of coherent dedispersion and the narrow synthesised beam of the Westerbork Synthesis Radio Telescope resulted in a sensitive observation. Our improved sensitivity and resolution allow us to confirm the presence of a precursor to the interpulse at these frequencies. We also detected more than 1000 giant pulses and find that the interpulse precursor component shows no giant pulse emission. Therefore, we attribute it to a similar emission source as the precursor to the mainpulse. Together these precursors might be the normal emission seen from the majority of radio pulsars. From the dispersion-free giant pulses, we find that the emission rate is  ~10–20 × 10^-3 s^-1 and the scatter timescale in the range of  ~1.5–5.6 ms. We further find that the radio flux of the pulsar is 6–11 Jy in this frequency range.