A GIANT SAMPLE OF GIANT PULSES FROM THE CRAB PULSAR

Abstract

We observed the Crab pulsar with the 43-m telescope in Green Bank, WV over a\ntimespan of 15 months. In total we obtained 100 hours of data at 1.2 GHz and\nseven hours at 330 MHz, resulting in a sample of about 95000 giant pulses\n(GPs). This is the largest sample, to date, of GPs from the Crab pulsar taken\nwith the same telescope and backend and analyzed as one data set. We calculated\npower-law fits to amplitude distributions for main pulse (MP) and interpulse\n(IP) GPs, resulting in indices in the range of 2.1-3.1 for MP GPs at 1.2 GHz\nand in the range of 2.5-3.0 and 2.4-3.1 for MP and IP GPs at 330 MHz. We also\ncorrelated the GPs at 1.2 GHz with GPs from the Robert C. Byrd Green Bank\nTelescope (GBT), which were obtained simultaneously at a higher frequency (8.9\nGHz) over a span of 26 hours. In total, 7933 GPs from the 43-m telescope at 1.2\nGHz and 39900 GPs from the GBT were recorded during these contemporaneous\nobservations. At 1.2 GHz, 236 (3%) MP GPs and 23 (5%) IP GPs were detected at\n8.9 GHz, both with zero chance probability. Another 15 (4%) low-frequency IP\nGPs were detected within one spin period of high-frequency IP GPs, with a\nchance probability of 9%. This indicates that the emission processes at high\nand low radio frequencies are related, despite significant pulse profile shape\ndifferences. The 43-m GPs were also correlated with Fermi gamma-ray photons to\nsee if increased pair production in the magnetosphere is the mechanism\nresponsible for GP emission. A total of 92022 GPs and 393 gamma-ray photons\nwere used in this correlation analysis. No significant correlations were found\nbetween GPs and gamma-ray photons. This indicates that increased pair\nproduction in the magnetosphere is likely not the dominant cause of GPs.\nPossible methods of GP production may be increased coherence of synchrotron\nemission or changes in beaming direction.\n