GCN Circular 40891
Subject
Fermi GBM Triggers 250702B, C, D and E are likely from the same source
Event
Date
2025-07-02T19:04:27Z (9 months ago)
Edited On
2025-07-02T19:10:12Z (9 months ago)
From
eliza.neights@gmail.com
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov>
Via
Web form
E. Neights (GWU, NASA GSFC), O.J. Roberts (USRA, NASA MSFC), E. Burns (LSU), P. Veres (UAH) report on behalf of the Fermi-GBM Team:
At 13:09:02.03 UT, Fermi GBM triggered on GRB 250702D and was initially localized to an RA and Dec of 292.9 and 3.6 (19h, 31m, +03,33’; J2000), with an error of 14.7 deg. The light curve shows several peaks occurring over ~60 seconds.
Since then, an additional three bursts have triggered GBM with similar lightcurve characteristics and localizations. The trigger times and localizations are summarized as follows:
GRB Name MET (s) Time (UT) RA (deg) Dec (deg) Err (deg)
250702E 773166098 16:21:33.07 286.8 -17.7 11.6 (GCN 40890)
250702C 773160576 14:49:31.91 270.3 1.4 12.7 (GCN 40885)
250702B 773157370 13:56:05.77 286.0 -8.7 7.8 (GCN 40883)
250702D 773154547 13:09:02.03 292.9 3.6 14.7 (GCN 40886)
Despite the similar position lying close to or on the galactic plane, we observe photons in the BGO up to 1 MeV, with the majority of the photons occurring in the 50-300 keV range, which suggest the source may not be a typical galactic source and might be an ultra-long GRB or another source class. If a GRB origin is confirmed, it is 11.5 ks long, making it one of the longest ultra-long GRBs detected.
The combined GBM skymap can be found here: https://zenodo.org/records/15793558. The skymaps are all associated with each other with confidence between 89.2 and 98.5%.
There were no joint-GW detections during these triggered times.
We strongly suggest follow-up of the region to determine the nature of the source over multiple wavelengths.