An X-ray map of SN 1006 from the Einstein Observatory

The remnant of the supernova explosion of AD 1006 has been observed in the energy range 0.1–4 keV with the imaging proportional counter on the Einstein X-ray Observatory. The image, with resolution of order 1 arcmin, shows a limb brightened nebula, almost circular in outline, of radius R about 15 arcmin, and with enhanced emission in two quadrants (NE and SW). There are large spectral variations over the object, with the hardest spectra near the NE and SW limbs. We have modelled the source in three dimensions and find that the data require a shell of thickness $$\Delta R/R \lesssim0.1$$ of varying electron temperature ($$10^6 \lesssim T_\text e\lesssim 10^7\enspace \text K$$) and density ($$0.3\lesssim n_\text e\lesssim 6\enspace \text {cm}^{-3}$$) surrounding a fairly uniform interior ($$T_\text e\sim1.5\times10^6\text K,\enspace n_\text e\sim 1.0\enspace \text {cm}^{-3}$$). (The source distance is taken as 1 kpc.) The optical filaments lie parallel with the faintest (NW) edge of the X-ray shell and are about an arcminute outside the peak of the X-ray emission. It appears from the X-ray image that the expanding remnant has encountered a sharp density gradient in the ISM in this NW region. The mass visible in the X-ray image lies in the range ∼ 5–15M_⊙. It is argued that this high mass suggests SN 1006 may have been a more energetic supernova, of Type II. There is no evidence for a hot stellar remnant, the (3σ) upper limit blackbody temperature of 8 × 10⁵ K being the lowest obtained for any SNR examined to date.