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Astron. Astrophys. 359, 1107-1110 (2000)

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Inhomogeneous models for plerions: the surface brightness profile of the Crab Nebula

E. Amato 1,2, M. Salvati 3, R. Bandiera 3, F. Pacini 1,3 and L. Woltjer 3,4

1 Dipartimento di Astronomia e Scienza dello Spazio, Università di Firenze, Largo E. Fermi 5, 50125 Firenze, Italy
2 Department of Astronomy, 547 Campbell Hall, University of California, Berkeley, CA 94720, USA
3 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
4 Observatoire de Haute-Provence, 04870 Saint Michel l'Observatoire, France

Received 10 November 1999 / Accepted 9 May 2000

Abstract

We extend the homogeneous model for the synchrotron emission from plerions to allow more realistic predictions of the surface brightness distribution at different frequencies. Abandoning the assumption of a uniform particle distribution, we assume that particles are injected into the synchrotron nebula only in the vicinity of the pulsar. Their distribution is then determined by MHD propagation in a magnetic field of spatially constant but time-dependent intensity. This highly simplified model reproduces the integrated spectrum and the synchrotron surface brightness profile of the Crab Nebula at radio frequencies. However, when applied to higher frequencies, it underestimates the extension of the emitting region, suggesting that particle diffusion with respect to the magnetic field lines must occur.

Key words: ISM: supernova remnants – ISM: individual objects: Crab Nebula – radiation mechanisms: non-thermal

Send offprint requests to: E. Amato (amato@arcetri.astro.it)

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© European Southern Observatory (ESO) 2000

Online publication: July 13, 2000
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