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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.
Schurch, N.
Willingale, R.
Bernard, J. -. P.
Bocchino, F.
Lumb, D.
Decourchelle, A.
Ferrando, P.
Haberl, F.
Read, A. M.
Schaudel, D.
La Palombara N
Mereghetti, S.
Tiengo, A.
First Published: Jan-2001
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.
DOI Link: 10.1051/0004-6361:20000224
ISSN: 0004-6361
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
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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