Electron‐Ion Equilibration in Nonradiative Shocks Associated with SN 1006

The ultraviolet spectrum of SN 1006 observed by the Hopkins Ultraviolet Telescope (HUT) is modeled to infer the degree of electron-ion equilibration at the nonradiative shocks in the remnant. Such an approach is possible since the spectrum has lines (He II j1640) whose excitation is dominated by electrons, and others (C IV j1550, N V j1240, O VI j1036) in which protons and other ions are more important, and the intensity ratio between these is sensitive to the electron-ion temperature ratio. We nd substantially less than full equilibration, marginally consistent with existing plasma simulations but rather more suggestive of even lower equilibration than these studies would predict. The more stringent limits on the electron temperature resulting from this allow a more accurate determination of the distance to SN 1006. Our result is 1.8 ^0.3 kpc.