This is the definition of the ultimate torture.
It appears that this black hole has been slowly feasting on this dead star for at least a decade. Ouch!
"We have witnessed a star's spectacular and prolonged demise," said Dacheng Lin, a research scientist at UNH's Space Science Center and the study's lead author. "Dozens of these so-called tidal disruption events have been detected since the 1990s, but none that remained bright for nearly as long as this one."
The arXiv version of this paper can be found here.
Moral of the story: Never piss off a black hole!