GCN Circular 44615
Subject
GRB 260511B: GMG Optical Upper Limit
Event
Date
2026-05-15T04:58:07Z (5 months ago)
From
Rui-Zhi Li at Yunnan Observatories, CAS <liruizhi@ynao.ac.cn>
Via
email
R.-Z. Li, B.-T. Wang, F.-F. Song, J. Mao, J.-G. Wang and B. Wang (YNAO, CAS) report:
We observed the field of GRB 260511B (Godet et al., GCN 44543, T0 at 2026-05-11T11:00:32) using the GMG-2.4m telescope at the Lijiang Observatory.
The observation began at 2026-05-14 12:45:02, about 73.74 hours after the trigger.
The optical counterpart (Wu et al. GCN 44547, Sasada et al. GCN 44549, Jiang et al. GCN 44551, Wu et al. GCN 44552, Vijaykumar et al. GCN 44561, de Ugarte Postigo et al. GCN 44565, Lee et al. GCN 44567, Li et al. GCN 44568, Wang et al. GCN 44571, Belkin et al. GCN 44572, Adami et al. GCN 44573, Saccardi et al. GCN 44574, Rajabov et al. GCN 44576, Perez-Fournon et al. GCN 44577, Novotny et al. GCN 44580, Moskvitin et al. GCN 44582, Calapai et al. GCN 44592, Moskvitin et al. GCN 44600 and Liu et al. GCN 44610) of GRB 260511B was not detected in our r-band image.
The preliminary analysis results are shown as follows:
+-------------------------+----------------+---------------+----------+----------------+
| Start time [UTC] | Exposure [s] | Tmid-T0 [h] | Filter | 5-sigma U.L. |
+=========================+================+===============+==========+================+
| 2026-05-14 12:45:02.730 | 900 | 73.867 | r | 21.6 |
+-------------------------+----------------+---------------+----------+----------------+
The given magnitudes are derived based on calibrating against Pan-STARRS1 field stars.