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|Title:||The extended X-ray halo of the Crab-like SNR G21.5-0.9|
|Authors:||Warwick, R. S.|
Griffiths, R. G.
Bernard, J. -. P.
Read, A. M.
La Palombara N
|Publisher:||EDP Sciences for European Southern Observatory (ESO)|
|Citation:||Astronomy & Astrophysics, 2001, 365 (1)|
|Abstract:||Recent XMM-Newton observations reveal an extended ( $r \approx 150''$) 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 $\Gamma = 1.63 \pm 0.04$ in the core to $\Gamma = 2.45 \pm 0.06$ 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.|
|Rights:||Copyright © 2001 ESO. Reproduced with permission from Astronomy & Astrophysics, © ESO.|
|Appears in Collections:||Published Articles, Dept. of Physics and Astronomy|
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