  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 {\sigma}_e = 2.4 \pm 0.3 eV,
corresponding to an oxygen temperature of 275$^{+72}_{-63}$ 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
H{\alpha} and X-ray synchrotron geometry, in that the H{\alpha} emission peaks
downstream of the synchrotron emission. This may be an indication for a
peculiar H{\alpha} shock, in which the density is lower and neutral fraction
are higher than in other supernova remnants, resulting in a peak in H{\alpha}
emission further downstream of the shock.
