The standard candles are Type Ia supernova which are when white dwarfs exceed the Chandrasekhar mass and become neutron stars. It is thought that when neutron stars exceed the maximum mass of a neutron star (which is not well known, by the way) they form a gamma-ray burst.

I think it's type 1a. There was a discussion on this recently after a new supernova observation.

https://news.ycombinator.com/item?id=7104056

Basically it's unknown if it is a two star system where the neutron consumes the partner, or a three star system where two neutron stars collide head on.