GOTO identification and broad-band modelling of the counterpart to the SVOM GRB 250818B
The Franco-Chinese SVOM mission,
launched in 2024, hosts four main instruments optimised for following up
gamma ray bursts.
Our
Gravitational-wave Optical Transient
Observer (GOTO) project is now following up SVOM triggers in addition
to other high-energy satellites, and identified the optical counterpart
to GRB 250818B
(GOTO25fzq/AT 2025ukm)
in observations taken just over half an hour after the trigger.
Monash PhD student Sergey Belkin led the followup effort on this object, gathering and compiling multiband optical/near-IR, X-ray and radio data covering the afterglow. A likely redshift of z=1.216 derived from Keck spectroscopy made for a challenging search for a galaxy host, and ultimately none was found. Sergey's paper reporting the exhaustive analysis of this event has now been published by MNRAS.