TITLE: GCN CIRCULAR NUMBER: 39319 SUBJECT: EP250212a: Xinglong optical upper limit DATE: 25/02/14 03:31:35 GMT FROM: EP Team at NAOC/CAS ep_ta@bao.ac.cn

Junjie-Jin(NAOC), Haiyang-Mu(NAOC), Yinan-Zhu(NAOC), Jiajun-Jia(NAOC), YuGuang-Sun(NAOC), Zhou-Fan(NAOC), Hong-Wu(NAOC) report on behalf of a large collaboration: Following the detection of EP250212a by EP-WXT (Li et al., GCN 39308), we observed the field of EP250212a using Tsinghua-NAOC 0.8-m telescope (TNT) located at Xinglong, Hebei, China. A total of 3600 s N-band exposures were taken , with a median observation time of 2025-02-12 14:27:29, approximately 6.72 hours after the EP trigger. No optical counterpart was detected, with a 5-sigma limiting magnitude of 20.7, calibrated with Pan-STARRS sources in the field. Later，We observed the EP250212a by the Xinglong 2.16-m telescope located at Xinglong, Hebei, China. A total of 1200 s N-band exposures were taken , with a median observation time of 2025-02-12 16:15:05, approximately 8.52 hours after the EP trigger. No optical counterpart was detected, with a 5-sigma limiting magnitude of 21.7, calibrated with Pan-STARRS sources in the field.

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