Shock breakout theory

Understand

The earliest supernova (SN) emission is produced when the optical depth of the plasma lying ahead of the shock, which ejects the envelope, drops below c/v, where v is the shock velocity.

• This "breakout" may occur when the shock reaches the edge of the star, producing a bright X-ray/UV flash on time scales of seconds to a fraction of an hour, followed by UV/optical "cooling" emission from the expanding cooling envelope on a day time-scale.
• If the optical depth of circumstellar material (CSM) ejected from the progenitor star prior to the explosion is larger than c/v, the breakout will take place at larger radii, within the CSM, extending its duration to days time scale.
• The properties of the early, breakout and cooling, emission carry unique signatures of the structure of the progenitor star (e.g.