GCN Circular 45508
Subject
GRB 260903A: NOT optical observations and afterglow fading
Event
Date
2026-09-04T00:54:37Z (12 hours ago)
From
Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk>
Via
Web form
D. B. Malesani (DAWN/NBI), J. An (NAOC), G. Corcoran (UCD), A. Saccardi (CEA/Irfu), F. Mustafaj (NOT), O. Stalder (NOT), report on behalf of a larger collaboration:
We observed the optical counterpart (Li et al., GCN 45504; Saccardi et al., GCN 45505) of the SVOM/ECLAIRs GRB 260903A (Brunet et al., GCN 45499) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. A total of 3x300 s observations were secured in the SDSS r band.
The optical afterglow is detected in our images. Preliminary photometry against the Pan-STARRS catalog yields a magnitude r = 22.88 +- 0.16 (AB) on 2026 Sep 4.00 UT, that is 11.45 hr after the trigger.
Our measurement indicates significant fading compared to previously reported measurements (Li et al., GCN 45504; Saccardi et al., GCN 45505), thus confirming that this object is the afterglow of GRB 260903A.