2019ApJ...875..123Y -
Astrophys. J., 875, 123-123 (2019/April-3)
The energy-dependent γ-ray morphology of the Crab Nebula observed with the Fermi Large Area Telescope.
YEUNG P.K.H. and HORNS D.
Abstract (from CDS):
The Crab Nebula is a bright emitter of non-thermal radiation across the entire accessible range of wavelengths. The spatial and spectral structures of the synchrotron nebula are well-resolved from radio to hard X-ray emission. The unpulsed emission at GeV-TeV energies is mostly produced via inverse-Compton scattering of energetic electrons with the synchrotron-emitted photons. The spatial structure observed at these energies provides insights into the distribution of electrons and indirectly constrains the so-far unknown structure of the magnetic field in the nebula. Analyzing the Large Area Telescope (LAT) data accumulated over ∼9.1 yr with a properly refined model for the Crab pulsar's spectrum, we determined the 68% containment radius (R68) of the Crab Nebula to be (0.0330±0.0025stat–0.0075+0.0012sys)○ (1′ / . 98±0′ / . 15stat–0.^′45+0_.^′07^sys) in the 5-500 GeV band. The estimated systematic uncertainty is based on two factors: (1) different analysis methods, morphological models and event types, and (2) the point-spread function evaluated with observations of Mkn 421. When comparing the Fermi-LAT and High Energy Stereoscopic System results on the spatial extension, we find evidence for an energy-dependent shrinking of the Crab Nebula's γ-ray extension (R68∝EIC^-α^, where α=0.155±0.035stat-0.037sys).
Abstract Copyright:
© 2019. The American Astronomical Society. All rights reserved.
Journal keyword(s):
gamma rays: ISM - ISM: individual objects: Crab Nebula
Errata:
erratum vol. 909, art. 221 (2021)
Simbad objects:
5
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