The Plerionic Supernova Remnant G21.5-0.9 Powered by PSR J1833-1034: New Spectroscopic and Imaging Results Revealed with the Chandra X-ray Observatory

Abstract

(Abridged) In 1999, Chandra revealed a 150"-radius X-ray halo surrounding the 40"-radius PWN G21.5-0.9. A 2005 imaging study showed that the halo is limb-brightened, and suggested this feature is a candidate for the long-sought SNR shell. We present a spectral analysis of G21.5-0.9, using the longest effective observation to date (578.6 ks with ACIS, 278.4 ks with HRC) to study unresolved questions about the spectral nature of remnant features, such as the limb-brightening of the X-ray halo and the bright knot in the northern part of the halo. The Chandra analysis favours the non-thermal interpretation of the limb. Its spectrum is well fit with a power-law model with a photon index $\Gamma$ = 2.13 (1.94-2.33) and a luminosity of L_x (0.5-8 keV) = (2.3 +/- 0.6) x 10^33 erg/s (at an assumed distance of 5.0 kpc). An srcut model was also used to fit the spectrum between radio and X-ray energies. We find that the maximum energy to which electrons are accelerated at the shock ranges from ~60-130 TeV (B/10$\mu$G)^(-1/2), where B is the magnetic field in units of $\mu$G. For the northern knot, we constrain previous models and find that a two-component power-law (or srcut) + pshock model provides an adequate fit, with the pshock model requiring a very low ionization timescale and solar abundances for Mg and Si. Our spectroscopic study of J1833-1034, the highly energetic pulsar powering G21.5-0.9, shows that its spectrum is dominated by hard non-thermal X-ray emission with some evidence of a thermal component that represents ~9% of the observed non-thermal emission and that suggests non-standard rapid cooling of the neutron star. Finally, the ACIS and HRC-I images provide the first evidence for variability in the PWN, a property observed in other PWNe such as the Crab and Vela.

Accepted by ApJ. 38 pages using aastex.cls - including 4 tables and 14 figures (figures 1, 2, and 10-13 are in colour). Resolution of figures 1, 10, 11, and 13 have been reduced for astro-ph submission only. The original full-resolution version can be downloaded from: http://www.physics.umanitoba.ca/~samar/ms-G21.pdf

References in corpus (6)

• The Distances of SNRs Kes 69 and G21.5-0.9 from HI and 13CO Spectra
• The Expansion and Radio Spectral Index of G21.5-0.9: Is PSR J1833-1034 the Youngest Pulsar?
• Using Chandra to Unveil the High-Energy Properties of the High-Magnetic Field Radio Pulsar J1119-6127
• A Shell of Thermal X-ray Emission Associated with the Young Crab-like Remnant 3C58
• Hard X-ray observations of PSR J1833-1034 and its associated pulsar wind nebula
• The discovery of PSR J1833-1034 : the pulsar associated with the supernova remnant G21.5-0.9

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