Geometry of the non-thermal emission in SN 1006

Abstract

Abstract. SN 1006 is the prototype of shell supernova remnants, in which non-thermal synchrotron emission dominates the X-ray spectrum. The non-thermal emission is due to the cosmic-ray electrons accelerated behind the blast wave. The X-ray synchrotron emission is due to the highest energy electrons, and is thus a tracer of the maximum energy electrons may reach behind a shock. We have put together all XMM-Newton observations to build a full map of SN 1006. The very low brightness above 2 keV in the interior indicates that the bright non-thermal limbs are polar caps rather than an equator. This implies that the ambient magnetic field runs southwest to northeast, along the Galactic plane. We used a combined VLA/Parkes radio map to anchor the spectrum at low energy, and model the spectra with synchrotron emission from a cut-off power-law electron distribution, plus a thermal component. We present radial and azimuthal profiles of the cut-off frequency. The cut-off frequency decreases steeply with radius towards the center and with position angle away from the maximum emission. The maximum energy reached by accelerated particles, as well as their number, must be higher at the bright limbs than elsewhere. This implies interesting constraints for acceleration at perpendicular shocks. Overall the XMM-Newton data is consistent with the model in which the magnetic field is amplified where acceleration is efficient.

First detection of VHEγ-rays from SN 1006 by HESS

“…Two different integration regions were defined a priori from the XMM-Newton data set (Rothenflug et al 2004): a map of the flux in the 2-4.5 keV energy range (to exclude thermal contamination) was smoothed with the HESS PSF, and regions which contained 80% of the flux were calculated. The two resulting regions, denoted as NE Region and SW Region, are displayed as white contours in Fig.…”

“…The HESS profile is compatible with a superposition of two Gaussian emission regions almost at 180 • from each other, respectively The white cross indicates the geometrical centre of the SNR obtained from XMM data as explained in the text and the dashed circles correspond to R ± dR as derived from the fit. The white star shows the centre of the circle encompassing the whole X-ray emission as derived by Rothenflug et al (2004) and the white triangle the centre derived by Cassam-Chenaï et al (2008) from Hα data. The white contours correspond to a constant X-ray intensity as derived from the XMM-Newton flux map and smoothed to the HESS point spread function, enclosing respectively 80%, 60%, 40% and 20% of the X-ray emission.…”

A simple model for electron plasma heating in supernova remnants

“…This velocity is in a good agreement with analogous velocity measurements by Smith et al (1991) which give v = 2200−3500 km s −1 . At this distance the SNR apparent size 15 (Rothenflug et al 2004) translates into a shock radius equal to r shock = 9.6 pc. A value for the ambient gas density equal to n = 0.15−0.25 cm −3 (in the north-western region) has been obtained by Acero et al (2007) from XMM X-ray observations.…”

Supernova remnants, planetary nebulae and superbubbles: Prospects for new XMM‐Newton observations

“…Using XMM-Newton, Rothenflug et al (2004) have shown very strong azimuthal variations that cannot be explained by variations of the magnetic compression alone. The maximum energy of the accelerated particles is higher at the bright synchrotron limbs than elsewhere.…”