Binary neutron star merger is not the only important stellar explosion due to the interaction between binary stars:

OBSERVE yonder binary system that consists of 2 low mass stars in close orbit. Notice that as the Primary reaches the red giant stage first the two stars share a common envelope which slows the orbital velocity and reduces the interstellar distance.

As the Primary dies, it blows off its outer layers, leaving its naked core of carbon and oxygen exposed as a white dwarf. It never achieved the mass needed to fuse that carbon and due to the lack of photon pressure the core has contracted under its own weight and become degenerate matter.

NOW let us fast-forward to the point where its companion becomes a red giant: The GREATLY EXPANDED outer shell reaches too close to its apparently dead companion. LO! Watch as the Dead Primary steals matter from Living Secondary. Slowly but steadily the mass of the dead star rises, until at 1.4M the density and temperature of its core reaches the ignition temperature for CARBON DETONATION and thanks to the inexpandable nature of the degenerate matter a runaway thermo-nuclear reaction takes hold.

BEHOLD!: the core temperature rises to billions of degrees, synthesising half a solar mass of the elements around iron in a few brief seconds as the star blows itself to SMITHEREENS in a supernova.

KABOOM!

ALL of the products of that explosion are distributed into the ISM, increasing its metallicity, especially of the elements around Fe.

The Celestial Comedian is itching to make a visual pun. WATCH as he finds a type 1a candidate situated on top of a dust cloud shaped like a candle stick. When carbon detonation occurs he uses the light from the explosion to read a book in bed at a distance of 1,000 light years. The same flux as he would have had from a standard candle at 1m...