The collapsing star Amargosa in 2371
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 Veridian III. (Star Trek Generations)
According to the Star Trek: Star Charts, on page 64, Amargosa was located in the Beta Quadrant. This star was classified in 2378 as a neutron star/pulsar.