TITLE: GCN CIRCULAR NUMBER: 33101 SUBJECT: IceCube-221223A: BOOTES-4/MET Optical Observations DATE: 22/12/25 07:48:52 GMT FROM: Dingrong Xiong at Yunnan Observatories of CAS, China D. R. Xiong, J. M. Bai, Y. F. Fan, K. Ye, C. J. Wang, Y. X. Xin, B. L. Lun, J. R. Mao, X. H. Zhao, L. Xu, X. G. Yu, K. X. Lu, X. Ding, D. Q. Wang (Yunnan Observatories), A. J. Castro-Tirado, E. Fernandez-Garcia, Y. D. Hu (IAA-CSIC) and C. J. Perez del Pulgar (UMA) on behalf of the BOOTES team: On 22-12-23 at 07:43:00.52 UT (T0) IceCube detected a track-like event with a high probability of being of astrophysical origin (GCN 33094). The gamma-ray source 4FGL J2322.7+3436 is located within the preliminary 90% uncertainty radius of the event (GCN 33094, 33100). We observed the gamma-ray source 4FGL J2322.7+3436 using BOOTES-4/MET 0.6m automatic optical telescope. During our observation period, this target is darker in optical SDSS-i band compared to result of SDSS DR16 (15.32 mag). From the 23rd to the 24th, the target has a small brightening. The magnitudes were calculated using four stars in the same frame and the SDSS DR16 catalogue as reference. The SDSS-i band magnitudes (without being corrected for Galactic extinction) are given as follows. MJD-T0 (day) | UT(start) | Magnitude (error) | Exposure Time ------------------------------------------------------------------------------ 0.394 | 22-12-23T17:10:40.800 | 15.565 (0.07) | 180s 0.397 | 22-12-23T17:14:47.990 | 15.585 (0.07) | 180s 0.4 | 22-12-23T17:18:58.982 | 15.545 (0.07) | 180s 0.403 | 22-12-23T17:23:11.962 | 15.565 (0.08) | 180s 0.406 | 22-12-23T17:27:18.979 | 15.455 (0.08) | 180s 1.263 | 22-12-24T14:01:26.026 | 15.401 (0.04) | 180s 1.267 | 22-12-24T14:06:55.037 | 15.427 (0.04) | 180s ------------------------------------------------------------------------------ There was no optical source within best-fit position of IceCube-221223A. The upper limit of magnitude (without being corrected for Galactic extinction) is 20.18 +/- 0.06 (clear filter, exposure of 30*60s, 22-12-23T11:19:55.746 UT). -------------------------------------------------------------------------------------------------------------- The Burst Optical Observer and Transient Exploring System (BOOTES) is a world-wide automatic telescope network which aims to repaid follow-up of transient and astrophysical sources in the sky for which the first station was installed in 1998 (Hu et al. 2021). The fourth station of the BOOTE Network, BOOTES-4/MET, is located at the Lijiang Observatory of the Yunnan Observatories of China (Xiong et al. 2020). We acknowledge the support of these staffs from the BOOTES telescope networks.