Question

which of these is a possible source of gamma - ray bursts that astronomers have observed using space - based telescopes?
neutron stars merging together in a high - redshift galaxy
mass being pulled from one star onto its black - hole binary companion
a massive star in the milky way exploding as a hypernova
material being fed into a supermassive black hole at the center of a galaxy

Explanation:

Gamma - ray bursts are extremely energetic explosions. Neutron - star mergers, hypernovae of massive stars, accretion onto black holes (both stellar - mass and supermassive) can all be sources. Neutron stars merging together in a high - redshift galaxy can release a huge amount of energy in the form of gamma - rays. Mass transfer in a star - black hole binary can also power gamma - ray emissions. A hypernova explosion of a massive star in the Milky Way can produce gamma - ray bursts. And material being fed into a supermassive black hole at the center of a galaxy can generate gamma - ray outbursts.

Answer:

All of the above options are possible sources of gamma - ray bursts.