A SMS is expected to have a radius of roughly 1 billion kilometres and a lifespan of only ~1 million years. Once the SMS exhausts its nuclear fuel, it starts collapsing into a massive black hole. During the collapse, relativistic jets can be launched from the accretion disk around the growing, nascent black hole. The relativistic jets can break through the star’s surface to produce an ultra-long gamma ray burst (ULGRB) with duration of ~10,000 to 1,000,000 seconds. Gamma-ray bursts (GRBs) are generally classified into short gamma-ray bursts (SGRBs) with durations under 2 seconds and long gamma-ray bursts (LGRBs) with duration greater than 2 seconds. ULGRBs are a third class of GRBs with durations of ~10,000 seconds or more. The collapse of SMSs into massive black holes may be observed as ULGRBs.
Matsumoto et al. (2015), “Direct Collapse Black Holes Can Launch Gamma-Ray Bursts and Get Fat to Supermassive Black Holes?”, arXiv:1506.05802 [astro-ph.HE]