Simultaneous Dual‐Frequency Observations of Giant Pulses from the Crab Pulsar
| Autor: | Timothy H. Hankins, D. A. Moffett, Don Backer, Shauna Sallmen, S. C. Lundgren |
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| Rok vydání: | 1999 |
| Předmět: |
Physics
Nebula 010308 nuclear & particles physics Crab Pulsar Astrophysics::High Energy Astrophysical Phenomena Astrophysics (astro-ph) Astrophysics::Instrumentation and Methods for Astrophysics FOS: Physical sciences Magnetosphere Astronomy and Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics Plasma Astrophysics 01 natural sciences Supernova Pulsar Space and Planetary Science Rise time 0103 physical sciences Exponential decay 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics |
| Zdroj: | The Astrophysical Journal. 517:460-471 |
| ISSN: | 1538-4357 0004-637X |
| DOI: | 10.1086/307183 |
| Popis: | Simultaneous measurements of giant pulses from the Crab pulsar were taken at two widely spaced frequencies using the real-time detection of a giant pulse at 1.4 GHz at the Very Large Array to trigger the observation of that same pulse at 0.6 GHz at a 25-m telescope in Green Bank, WV. Interstellar dispersion of the signals provided the necessary time to communicate the trigger across the country via the Internet. About 70% of the pulses are seen at both 1.4 GHz and 0.6 GHz, implying an emission mechanism bandwidth of at least 0.8 GHz at 1 GHz for pulse structure on time scales of one to ten microseconds. The arrival times at both frequencies display a jitter of 100 microseconds within the window defined by the average main pulse profile and are tightly correlated. This tight correlation places limits on both the emission mechanism and on frequency dependent propagation within the magnetosphere. At 1.4 GHz the giant pulses are resolved into several, closely spaced components. Simultaneous observations at 1.4 GHz and 4.9 GHz show that the component splitting is frequency independent. We conclude that the multiplicity of components is intrinsic to the emission from the pulsar, and reject the hypothesis that this is the result of multiple imaging as the signal propagates through the perturbed thermal plasma in the surrounding nebula. At both 1.4 GHz and 0.6 GHz the pulses are characterized by a fast rise time and an exponential decay time which are correlated. The pulse broadening with its exponential decay form is most likely the result of multipath propagation in intervening ionized gas. Comment: LaTeX, 18 pages, 7 figures, accepted for publication in The Astrophysical Journal |
| Databáze: | OpenAIRE |
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