The northwestern ejecta knot in SN 1006

Abstract

Aims: We want to probe the physics of fast collision-less shocks in supernova remnants. In particular, we are interested in the non-equilibration of temperatures and particle acceleration. Specifically, we aim to measure the oxygen temperature with regards to the electron temperature. In addition, we search for synchrotron emission in the northwestern thermal rim. Methods: This study is part of a dedicated deep observational project of SN 1006 using XMM-Newton, which provides us with currently the best resolution spectra of the bright northwestern oxygen knot. We aim to use the reflection grating spectrometer to measure the thermal broadening of the O vii line triplet by convolving the emission profile of the remnant with the response matrix. Results: The line broadening was measured to be σ_e = 2.4 \pm 0.3 eV, corresponding to an oxygen temperature of 275${}_{-63}^{+72}$ keV. From the EPIC spectra we obtain an electron temperature of 1.35 \pm 0.10 keV. The difference in temperature between the species provides further evidence of non-equilibration of temperatures in a shock. In addition, we find evidence for a bow shock that emits X-ray synchrotron radiation, which is at odds with the general idea that due to the magnetic field orientation only in the NE and SW region X-ray synchrotron radiation should be emitted. We find an unusual Hα and X-ray synchrotron geometry, in that the Hα emission peaks downstream of the synchrotron emission. This may be an indication for a peculiar Hα shock, in which the density is lower and neutral fraction are higher than in other supernova remnants, resulting in a peak in Hα emission further downstream of the shock.

6 pages, 7 figures. Accepted for publication in A&A

References in corpus (7)

• Analytical solutions for energy spectra of electrons accelerated by nonrelativistic shock-waves in shell type supernova remnants
• First detection of VHE gamma-rays from SN 1006 by H.E.S.S
• Spatial Structure and Collisionless Electron Heating in Balmer-dominated Shocks
• Variation of cosmic ray injection across supernova shocks
• The gas density around SN 1006
• Fe XVII X-ray Line Ratios for Accurate Astrophysical Plasma Diagnostics
• XMM-Newton evidence of shocked ISM in SN 1006: indications of hadronic acceleration

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