TITLE:   GCN CIRCULAR
NUMBER:  45577
SUBJECT: GRB 260915A: NOT optical upper limit
DATE:    26/09/15 07:53:10 GMT
FROM:    Zipei Zhu at NAOC <zpzhu@nao.cas.cn>

Z. Zhu, J. An, D. Xu (NAOC), A. Saccardi (CEA/Irfu), D. B. Malesani (DAWN/NBI), V. Neustroev (NOT), V. Vuolteenaho (NOT), report on behalf of a larger collaboration:

We observed the field of GRB 260915A detected by SVOM/ECLAIRS (Liang et al., GCN 45570), using the ALFOSC camera mounted on the Nordic Optical Telescope (NOT). We obtained 5x200 s exposures in the SDSS z-band starting at 05:21 UT on 2026-09-15 (about 4.2 hr after the trigger).

No uncatalogued optical transient is detected in the stacked image within the SVOM/ECLAIRs error region in agreement with previous observations (Yin et al., GCN 45573; Wu et al., GCN 45575), down to a 3-sigma limiting magnitude of z ~ 21.5, calibrated with Pan-STARRS DR2 stars in the field and not corrected for Galactic extinction.