Resolving the Emission Regions of the Crab Pulsar’s Giant Pulses. II. Evidence for Relativistic Motion
Artikel i vetenskaplig tidskrift, 2023

The Crab Pulsar is the prime example of an emitter of giant pulses. These short, very bright pulses are thought to originate near the light cylinder, at ∼1600 km from the pulsar. The pulsar’s location inside the Crab Nebula offers an unusual opportunity to resolve the emission regions, using the nebula, which scatters radio waves, as a lens. We attempt to do this using a sample of 61,998 giant pulses found in coherently combined European VLBI network observations at 18 cm. These were taken at times of relatively strong scattering and hence good effective resolution. From correlations between pulse spectra, we show that the giant pulse emission regions are indeed resolved. We infer apparent diameters of ∼2000 and ∼2400 km for the main and interpulse components, respectively, and show that with these sizes the correlation amplitudes and decorrelation timescales and bandwidths can be understood quantitatively, both in our observations and in previous ones. Using pulse-spectra statistics and correlations between polarizations, we also show that the nebula resolves the nanoshots that comprise individual giant pulses. The implied diameters of ∼1100 km far exceed light-travel-time estimates, suggesting the emitting plasma is moving relativistically, with γ ≃ 104, as inferred previously from drifting bands during the scattering tail of a giant pulse. If so, the emission happens over a region extended along the line of sight by ∼107 km. We conclude that relativistic motion likely is important for producing giant pulses, and may be similarly for other sources of short, bright radio emission, such as fast radio bursts.

Författare

Rebecca Lin

University of Toronto

Marten H. van Kerkwijk

University of Toronto

Robert Main

Max-Planck-Gesellschaft

Nikhil Mahajan

University of Toronto

U. L. Pen

University of Toronto

Canadian Institute for Advanced Research

Institut canadien d'astrophysique théorique

Academia Sinica

Perimeter Institute for Theoretical Physics

Franz Kirsten

Netherlands Institute for Radio Astronomy (ASTRON)

Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 945 2 115

Ämneskategorier

Astronomi, astrofysik och kosmologi

Atom- och molekylfysik och optik

Fusion, plasma och rymdfysik

DOI

10.3847/1538-4357/acba95

Mer information

Senast uppdaterat

2023-04-13