TITLE: GCN CIRCULAR NUMBER: 37348 SUBJECT: GRB 240828B: GWAC-F50A optical upper limit DATE: 24/08/30 06:14:43 GMT FROM: Liping Xin at NAOC, SVOM xlp@nao.cas.cn

SVOM/GWAC-F50A team：L.P.Xin(NAOC), Y.G.Yang(HNU), X.H.Han, X.M.Lu, R.S.Zhang, Y.Xu, Y.J.Xiao, P.P.Zhang, H.B.Cai, Y.L.Qiu, H.L.Li,C.Wu, L.Lan, W.J.Xie, J.Y.Wei(NAOC),J.Wang,X.G.Wang(GXU)

SVOM JSWG: Jian-Yan Wei (NAOC, China), Bertrand Cordier (CEA, F), Shuang-Nan Zhang (IHEP, CN), Stephane Basa (LAM, F), Jean-Luc Attéia (IRAP, F), Arnaud Claret (CEA, F), Zi-Gao Dai (USTC, CN), Frederic Daigne (IAP, F), Jin-Song Deng (NAOC, CN), Andrea Goldwurm (APC, F), Diego Götz (CEA, F), Xu-Hui Han (NAOC, CN), Cyril Lachaud (APC, F), En-Wei Liang (GXU, CN), Yu-Lei Qiu (NAOC, CN), Susanna Vergani (Obs.Paris, F), Jing Wang (NAOC, CN), Chao Wu(NAOC, CN), Li-Ping Xin (NAOC,CN), Bing Zhang (UNLV, CN)

We began to observe GRB 240828B (Le Provost et al., GCN 37318) detected by SVOM/ECLAIRs, with GWAC-F50A telescope at Xinglong station,China,at 16:45:50(UT), August 28,2024, about 3.55 hours after the burst. The weather was not good.

After stacking 20*100 seconds, no any new sources were detected in our stacked image within the X-ray afterglow error circles (Page et al. GCN 37334) down to a limit magnitude of 18.5 mag in R band at the mid-time of 3.83 hours post the burst, calibrated to several nearby USNO B1.0 stars.

We acknowledge the excellent support from observation assistant Yangtong Zheng and Winlong Dong.

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