TITLE: GCN CIRCULAR NUMBER: 40366 SUBJECT: GRB 250506A: Xinglong 2.16m optical upper limit DATE: 25/05/06 16:04:35 GMT FROM: Liping Xin at NAOC, SVOM xlp@nao.cas.cn

L. P. Xin, J. Zhen, J. Wang, H. L. Li, Y. L. Qiu, C. Wu, X. H. Han, Y. Xu, P. P. Zhang, Y. J. Xiao, L. Lan, W. J. Xie, J. S. Deng, J. Y. Wei (NAOC) report on behalf of SVOM follow-up team:

We observed the field of GRB 250506A (Wang et al., GCN 40358; Maggi et al., GCN 40364; Fermi team GCN 4035). using the 2.16-m telescope located at Xinglong observatory, China, equipped with the BFOSC camera. The weather is not good. We obtained 2*200s and 7x300s frames in R-band, starting at 14:00:19 UT on 2025-05-06,about 11.65 hrs after the trigger.

No any uncatalogued sources were detected within the error box of EP/FXT(Zhang et al., GCN 40365) or SVOM/Eclairs or SVOM/MXT (Maggi et al., GCN 40364) in our stacked image, down to a 3 sigma limiting magnitude of R~21.0 mag, calibrated with the nearby PanSTARRS field.

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