https://www.reddit.com/r/space/comments/1pmdkbv/sarah_dalessi_a_fifthyear_student_in_the_college/
Sarah Dalessi, a fifth-year student at the University of Alabama in Huntsville, is lead author of a paper in The Astrophysical Journal on GRB 230307A. NASA’s Fermi Gamma-ray Burst Monitor caught that burst in March 2023.
The team estimates its jet moved at 99.99998% of the speed of light, a Lorentz factor of about 1,600. UAH calls it the fastest gamma-ray burst ever recorded. The burst was also exceptionally bright and linked to a kilonova from merging neutron stars.
Fair caveat: jet speeds come from models, and the value depends on how the emission is interpreted. Other bursts, like GRB 090510, have lower limits above 1,000. So “fastest” means the highest estimate so far, not a settled record.
Source: www.reddit.com · Also: UAH · Paper (ApJ) · arXiv preprint