Neutron stars are one of the possible end-products of stellar evolution.
If, following its terminal stages, the remnant mass of a star is between 1.4 and 2 to 3 solar masses, the star will collapse into a neutron star, a body with a radius of 10 to 15 kilometers, with a core so dense that its component protons and electrons have merged into neutrons. The optical spectra did not show any emission lines, and no variations on time scales of minutes were observed for 1 hour during the decline phase. The authors suggest the observations are incompatible with the fireball and afterglow models of gamma ray bursts, and that another physical mechanism may be respons- ible for the constant phase seen the first few hours after the burst occurs.