Volume 365, Number 1, January 2001
First Results from XMM-Newton
|Page(s)||L248 - L253|
|Published online||15 January 2001|
The extended X-ray halo of the Crab-like SNR G21.5-0.9
Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
2 Institute d'Astrophysique Spatiale, Orsay, France
3 Space Science Department, ESTEC, 2200 AG Noordwijk, The Netherlands
4 Service d'Astrophysique, CEA Saclay, 91191 Gif-sur-Yvette, France
5 Max-Planck-Institut für extraterrestrische Physik, 85740, Garching, Germany
6 Istituto di Fisica Cosmica "G. Occhialini", CNR, 20133 Milano, Italy
7 XMM-SOC, Villafranca Satellite Tracking Station, 28080 Madrid, Spain
Corresponding author: R. S. Warwick, firstname.lastname@example.org
Accepted: 9 November 2000
Recent XMM-Newton observations reveal an extended () low-surface brightness X-ray halo in the supernova remnant G21.5-0.9. The near circular symmetry, the lack of any limb brightening and the non-thermal spectral form, all favour an interpretation of this outer halo as an extension of the central synchrotron nebula rather than as a shell formed by the supernova blast wave and ejecta. The X-ray spectrum of the nebula exhibits a marked spectral softening with radius, with the power-law spectral index varying from in the core to at the edge of the halo. Similar spectral trends are seen in other Crab-like remnants and reflect the impact of the synchrotron radiation losses on very high energy electrons as they diffuse out from the inner nebula. A preliminary timing analysis provides no evidence for any pulsed X-ray emission from the core of G21.5-0.9.
Key words: ISM: individual (G21.5-0.9) / supernova remnants / X-rays: ISM
© ESO, 2001
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