D. A. Leahy, K. Green, S. Ranasinghe
We present an analysis of ROSAT and CHANDRA ACIS X-ray observations of the gamma Cygni supernova remnant (G78.2+2.1, DR4) and also analyze radio HI absorption spectra. The ROSAT All-Sky-Survey image shows extended X-ray emission from G78.2+2.1 and also an adjacent limb-brightened shell on its northern boundary. A new mosaic created from ROSAT pointed PSPC data shows details of the X-ray emission over the entire face of G78.2+2.1, including X-ray bright features along the southern, eastern and northern rim but a faint center and a faint western rim. We assemble all available Chandra archival data to create a new mosaic which covers a large part of the northern rim and central regions of G78.2+2.1. The HI absorption spectrum is used to obtain a distance limit on the SNR of 2-4 kpc. Chandra spectral parameters are used to constrain the physical properties of G78.2+2.1: we find an X-ray temperature of 0.6-1.2 keV (90% error), and that the SNR is well explained by a Sedov model with age of 8000-16000 yr and blast energy of $0.5-4 \times 10^{51}$ erg. The two brightest hard spectrum sources in G78.2+2.1 are found to be an extragalactic background source and a power-law spectrum compact source. The compact source has an X-ray column density consistent with that of G78.2+2.1 and has also been identified recently as a TeV emitter. Spectra from the northern rim of the SNR include an additional low column density component, which is the same as that from an X-ray spectrum of the northern shell. Thus the northern shell overlaps the northern part of G78.2+2.1. The low column density of the northern shell is consistent with the distance of a B3 star at distance of 980 pc. A stellar wind bubble origin for this northern shell is proposed.
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http://arxiv.org/abs/1307.3151
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