GCN Circular 45505
Subject
GRB 260903A: LCO optical observations
Event
Date
2026-09-03T20:50:07Z (a day ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
A. Saccardi (CEA/Irfu), D. B. Malesani (DAWN/NBI and Radboud), M. Pillas (IAP), H. L. Li (NAOC), Y.X. Guan, S.J. Yin (GXU), C. Wu, L.P. Xin (NAOC), Y.Y. Shi (GXU), D. Turpin (CEA/Irfu), R.-C. Chen (NJU), T. Xiao (GXU) report on behalf of the SVOM mission team:
Following the report of an optical counterpart (Li et al., GCN 45504) of the SVOM GRB 260903A (Brunet et al., GCN 45499), we inspected again our images taken at the Siding Spring Observatory with the LCO telescope (Guan et al., GCN 45501; Guan et al., GCN 45503).
In total, three epochs of observations in the SDSS r filter were secured (the first and the second consisting of 3x200 s exposures while the third of 6x200 s). The optical counterpart is detected in all three epochs, and we measure the following magnitudes (calibrated against the Pan-STARRS catalog and not corrected for Galactic extinction):
r = 20.92 +/- 0.19 AB (mid-time 38.66 min after the trigger);
r = 20.46 +/- 0.19 AB (mid-time 2.30 hr after the trigger);
r = 21.8 +/- 0.4 AB (mid-time 2.74 hr after the trigger).
Overall, there is no strong evidence for variability, though the source is only barely detected in our last epoch, suggesting some fading compared to our earlier epochs and to the SVOM/VT measurement (Li et al., GCN 45504).
This project is funded by the SVOM collaboration.