GCN Circular 45890
Subject
GRB 261010A: NOT possible optical counterpart
Event
Date
2026-10-10T21:39:17Z (a day ago)
From
Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk>
Via
Web form
D. O’Neill (Birmingham), B. Schneider (LAM), D. B. Malesani (DAWN/NBI and Radboud), B. Gompertz (Birmingham), L. Izzo (INAF/OACN and DARK/NBI), A. Martin-Carrillo (UCD), N. R. Tanvir (Leicester), A. Schenone-Zanuzzi (NOT), report on behalf of a larger collaboration:
We observed the position of the Swift and Fermi GRB 261010A (Lien et al., GCN 45889; Fermi GBM team, GCN 45888) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started as soon as weather conditions cleared, on 2026 Oct 10.874 UT (1.7 hr after the GRB trigger).
Both by visual inspection and by digital image subtraction (versus Pan-STARRS and Legacy), we note the presence of a source not seen in archival imaging, with the following coordinates (J2000):
RA = 16:34:59.46
Dec = +26:34:57.4
This position is slightly (~2") offset from a red source visible in the Legacy Survey images; the relation between these two objects is unclear. After template subtraction, we measure r ~ 21.36 +- 0.06 (AB) for the new source (not corrected for Galactic extinction).
The above coordinates are ~7" off the centre of the currently best available Swift/XRT position, which has a quoted uncertainty of 3.6". The association of this object with GRB 261010A is therefore tentative at the moment, and awaits confirmation. Further observations are planned and encouraged.