Kavli Affiliate: Erin Kara
| First 5 Authors: Eliza Neights, Eliza Neights, , ,
| Summary:
Gamma-ray bursts are the most luminous electromagnetic events in the
universe. Their prompt gamma-ray emission has typical durations between a
fraction of a second and several minutes. A rare subset of these events have
durations in excess of a thousand seconds, referred to as ultra-long gamma-ray
bursts. Here, we report the discovery of the longest gamma-ray burst ever seen
with a ~25,000 s gamma-ray duration, GRB 250702B, and characterize this event
using data from four instruments in the InterPlanetary Network and the Monitor
of All-sky X-ray Image. We find a hard spectrum, subsecond variability, and
high total energy, which are only known to arise from ultrarelativistic jets
powered by a rapidly-spinning stellar-mass central engine. These properties and
the extreme duration are together incompatible with all confirmed gamma-ray
burst progenitors and nearly all models in the literature. This burst is
naturally explained with the helium merger model, where a field binary ends
when a black hole falls into a stripped star and proceeds to consume and
explode it from within. Under this paradigm, GRB 250702B adds to the growing
evidence that helium stars expand and that some ultra-long GRBs have similar
evolutionary pathways as collapsars, stellar-mass gravitational wave sources,
and potentially rare types of supernovae.
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