Kinematics of Crab Giant Pulses
Abstract
The Crab Pulsar's radio emission is unusual, consisting predominantly of giant pulses, with durations of about a microsecond but structure down to the nanosecond level, and brightness temperatures of up to 10³⁷ K. It is unclear how giant pulses are produced, but they likely originate near the pulsar's light cylinder, where corotating plasma approaches the speed of light. We report observations in the 400–800 MHz frequency band, where the pulses are broadened by scattering in the surrounding Crab Nebula. We find that some pulse frequency spectra show strong bands, which vary during the scattering tail, in one case showing a smooth upward drift. While the banding may simply reflect interference between nanosecond scale pulse components, the variation is surprising, as in the scattering tail the only difference is that the source is observed via slightly longer paths, bent by about an arcsecond in the nebula. The corresponding small change in viewing angle could nevertheless reproduce the observed drift by a change in Doppler shift, if the plasma that emitted the giant pulses moved highly relativistically, with a Lorentz factor γ ∼ 10⁴ (and without much spread in γ). If so, this would support models that appeal to highly relativistic plasma to transform ambient magnetic structures to coherent gigahertz radio emission, be it for giant pulses or for potentially related sources, such as fast radio bursts.
Additional Information
© 2021. The American Astronomical Society. Received 2021 June 11; revised 2021 July 12; accepted 2021 July 16; published 2021 October 11. A.B. thanks Thierry Serafin Nadeau and Rebecca Lin for help with the data reduction. The authors also thank Laura Newburgh and Andre Renard for their critical contributions to the ARO 46 m front-end and back-end systems, respectively, the latter and Tom Landecker for conducting the overlapping DRAO observations, Sasha Philippov, Maxim Lyutikov, Wadiasingh Zorawar, and Sterl Phinney for discussions about the theoretical interpretation, all members of the scintillometry group for lively discussions, and the referee for comments that helped make our manuscript clearer. U.-L.P. receives support from the Ontario Research Fund Research Excellence Program (ORF-RE), Natural Sciences and Engineering Research Council of Canada (NSERC) [funding reference number RGPIN-2019-067, CRD 523638-201, 555585-20], Canadian Institute for Advanced Research (CIFAR), Canadian Foundation for Innovation (CFI), Simons Foundation, Thoth Technology Inc., which owns and operates ARO, and Alexander von Humboldt Foundation. W.L. was supported by the David and Ellen Lee Fellowship at Caltech. Computations were performed on the Niagara supercomputer at the SciNet HPC Consortium. SciNet is funded by the Canada Foundation for Innovation, the Government of Ontario, Ontario Research Fund—Research Excellence, and the University of Toronto. Facilities: Algonquin Radio Observatory:46 m - , DRAO:26 m. - Software: astropy (Astropy Collaboration et al. 2018), Baseband ((van Kerkwijk et al. 2020)), tempo2 (Hobbs et al. 2006), numpy (Harris et al. 2020), matplotlib (Hunter 2007).Attached Files
Published - Bij_2021_ApJ_920_38.pdf
Accepted Version - 2105.08851.pdf
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Additional details
- Eprint ID
- 111623
- Resolver ID
- CaltechAUTHORS:20211022-225411884
- Ontario Research Fund-Research Excellence
- RGPIN-2019-067
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- CRD 523638-201
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- 555585-20
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- Canadian Institute for Advanced Research (CIFAR)
- Canada Foundation for Innovation
- Simons Foundation
- Thoth Technology Inc.
- Alexander von Humboldt Foundation
- David and Ellen Lee Postdoctoral Scholarship
- University of Toronto
- Created
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2021-10-22Created from EPrint's datestamp field
- Updated
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2021-10-26Created from EPrint's last_modified field