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Session 44 - The Local Diffuse ISM.
Display session, Tuesday, June 11
The ultraviolet spectrum of SN 1006 observed with the Hopkins Ultraviolet Telescope (HUT) on the Astro-2 mission in 1995 March is modeled to infer the degree of electron-ion equilibration at the non-radiative shock front in the remnant. Such an approach is possible since the spectrum has a line (He II 1640) whose excitation is dominated by electrons, and other lines (C IV 1550, N V 1240, and O VI 1036) where excitation by protons and other ions are more important. The intensity ratio between these lines is sensitive to the electron-ion temperature ratio. Our results are consistent with very little or no equilibration, and are only marginally consistent with existing plasma simulations that predict equilbration at the 20% level. The more stringent limits on the electron temperature (and hence shock velocity) resulting from this, combined with previous proper motion measurements, allows a more accurate determination of the distance to SN 1006. Our result is 1.8 \pm 0.3 kpc. From this we derive a diameter for SN 1006 of 15.7 \pm 2.6 pc and a mean expansion velocity of 7850 \pm 1300 km/s.
This work was supported by NASA Contract NAS 5-27000 to JHU, and NASA Grant NAG8-1074 to SAO.
Program listing for Tuesday