Almost every well-studied long gamma-ray burst has been associated with a rapidly star-forming galaxy and in many cases a core-collapse supernova as well . This links long GRBs with the deaths of massive stars . Almost every well-studied long gamma-ray burst has been associated with a rapidly star-forming galaxy and in many cases a core-collapse supernova as well , unambiguously linking long GRBs with the deaths of massive stars .