Amargosa

From Memory Alpha, the free Star Trek reference.

Amargosa was the primary star of the Amargosa system, studied by a Federation observatory where Dr. Tolian Soran developed his trilithium weapon. From the observatory, Soran launched the weapon into Amargosa in 2371 and collapsed the star, producing a level-12 shock wave that destroyed everything in the system.

The collapse of Amargosa had several repercussions in its sector of space. These effects included an increase in gamma emissions of .05%, gravitational forces were altered, forcing the USS Bozeman to make a minor course correction. The same forces altered the flight path of the Nexus ribbon as Soran had planned, as part of his attempt to bring the ribbon to a planet. (Star Trek Generations)

It is unknown if the collapse of the Amargosa star developed a quantum singularity, a dwarf star, or completely destroyed it.