The Ionization Effects of Shock Breakout in SN 1987A

The epoch of shock breakout in SN 1987A was almost certainly associated with the production of a pulse of UV photons with a characteristic temperature of order 100,000 K and a duration of 2-4 hr. It is proposed that this pulse has the characteristics required to ionize the precursor stellar wind, temporarily ionize any nearby remnants of the red giant wind, and can ionize the surrounding interstellar medium out to distances of several parsecs for several thousand years. These effects could provide transitory free-free absorption of the synchrotron radio source and may offer an explanation of the ionized knot seen in speckle interferometry. A similar but more powerful outburst could also be responsible for the highly ionized halo seen around the SMC supernova remnant 1E 0102.2-7219.