A series of images (Fig. 13-12, p. 338) shows the eruption of V838 Monocerotis.
The text says:
“An especially peculiar, and still poorly understood, eruption was V838 Monocerotis. This object brightened by a large amount, but probably for a different physical reason than normal novae. It was surrounded by many shells of dust that were “lit up” by the nova outburst. These “light echoes” evolved with time, as shells at different distances from the nova were successively illuminated. A consensus is emerging that its outbursts were from a violent merger of the two components of a binary star.”
Prof. Howard Bond of Penn State University writes (October 2014):
This consensus has been gaining even more popularity. The “Rosetta Stone” was the eruption of V1309 Scorpii in 2008…. It was in a field in the Galactic bulge that had been imaged by the OGLE project for about a decade before the outburst, and it turned out that the progenitor was a close binary, and it was even shown that its period was getting shorter up until the eruption.
A recent paper by Kochanek et al. estimates that a stellar merger occurs in the Milky Way about once every 5 years, so these are actually pretty common events.