Tidal Tail Ejection as a Signature of Type~Ia Supernovae from White Dwarf Mergers

Understand

The merger of two white dwarfs may be preceded by the ejection of some mass in "tidal tails", creating a circumstellar medium around the system.

• We consider the variety of observational signatures from this material, which depend on the lag time between the start of the merger and the ultimate explosion (assuming one occurs) of the system in a Type Ia supernova.
• If the time lag is fairly short, the interaction of the supernova ejecta with the tails could lead to detectable shock emission at radio, optical, and/or x-ray wavelengths.
• At somewhat later times, the tails produce relatively broad NaID absorption lines with velocity widths of order the white dwarf escape speed ($\sim 1000$ \kms).