{
  "body": "\nS.Y. Fu, S.Q. Jiang, J. An, Z.P. Zhu, X. Liu, D. Xu (NAOC), J.Z. Liu (XAO) report on behalf of a large collaboration:\n\nWe observed the field of GRB 240911A detected by SVOM/ECLAIRs (Schanne et al., GCN 37462), using the 50cm-A/B telescopes (50A, 50B) of the JinShan project, located at Altay, Xinjiang, China. Observations started at 16:27:18 UT on 2024-09-12, i.e., 19.8 hr after the trigger, and a series of frames were obtained in the Sloan g-, r-, i- and z-bands.\n\nNo new optical source is detected within the error circles of two uncatalogued Swift/XRT candidates (Williams et al., GCN 37483), down to the following 5-sigma upper limits:\n\nT_mid (UT) | T_mid (hr) | filter | 5-sigma U.L. (AB) \n----------------------------------------------------\n2024-09-12T17:18:03.5 | 20.65 | g | 21.1\n2024-09-12T16:42:30.0 | 20.06 | r | 21.1\n2024-09-12T16:49:22.0 | 20.18 | i | 20.1\n2024-09-12T17:24:54.0 | 20.77 | z | 18.8\n\ncalibrated with nearby PanSTARRS stars and not corrected for Galactic extinction. \n\nWe acknowledge the excellent support from X. Yao, S.W. Luo, and Z.K. Feng for enabling these observations.",
  "bibcode": "2024GCN.37489....1F",
  "eventId": "GRB 240911A",
  "submittedHow": "web",
  "subject": "GRB 240911A: JinShan optical upper limits on two Swift/XRT candidates",
  "createdOn": 1726244359839,
  "submitter": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
  "circularId": 37489,
  "format": "text/plain"
}