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| Paper: |
The Intriguing Plerionic Supernova Remnant G21.5-0.9 |
| Volume: |
271, Neutron Stars in Supernova Remnants |
| Page: |
217 |
| Authors: |
Safi-Harb, S.; Harrus, I. M.; Petre, R.; Pavlov, G. G.; Koptsevitch, A. B.; Sanwal, D. |
| Abstract: |
G21.5-0.9 is a center-brightened (or plerionic) supernova remnant (SNR) whose properties hint at the presence of a pulsar - yet no pulsations have been found at any wavelength. Early observations with Chandra led to the discovery of an extended component, making the SNR at least twice as big as originally thought. Our analysis indicates that this low-surface brightness extended component is non-thermal with a filamentary hard structure in the northern quadrant. We perform spatially-resolved spectroscopy and find no evidence of line emission using a 72-ksec exposure with ACIS-S. The 5 arcmin diameter remnant is well fitted with a power law with a photon index steepening from 1.5 to 2.7 (NH = 2.2 x 1022 cm-2). Using a 76-ksec exposure with the HRC, we derive an upper limit of 16% on the pulsed fraction from a putative pulsar. We also infer the parameters of the `hidden pulsar' in G21.5-0.9. This remnant remains unique and intriguing since it is, to date, the only candidate whose size is bigger in X-rays than in the radio. |
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