GCN Circular 42805
Subject
GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
Event
Date
2025-11-22T17:04:27Z (5 days ago)
From
Laura Cotter at University College Dublin <laura.cotter@ucdconnect.ie>
Via
Web form
L. Cotter, G. Corcoran (UCD), J. A. Chacon (PUC), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), report on behalf of a larger collaboration:
We observed the field of the transient event GRB 251122A / EP251122a detected by EP/WXT (Wang et al., GCN 42799) and by SVOM/ECLAIR (Lin et al., GCN 42800) with the Las Cumbres Observatory (LCO) network. We acquired six 300 s exposures in the r band starting on 2025-11-22 at 15:20:01 UTC (86 min after the EP/EXTtrigger).
No new source is detected within the error circle provided by EP/FXT (Wang et al., GCN 42799) and SVOM/MXT (Lin et al., GCN 42800). From the stacked r-band images we obtained a three sigma upper limit of r > 22.4 mag (AB), calibrated against the Pan-STARRS catalog and is not corrected for Galactic extinction.
We do not detect the candidate counterpart reported by Cheng et al. (GCN 42803), which was however fainter than our limit and observed at an earlier epoch. Our non-detection is also consistent with previous reports (Wu et al., GCN 42801; Lipunov et al., GCN 42802; Saccardi et al., GCN 42804).