TITLE: GCN CIRCULAR NUMBER: 33228 SUBJECT: IceCube-230122A: BOOTES-2/TELMA Optical Upper Limit DATE: 23/01/28 14:16:31 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 report: On 2023-01-22 03:50:02.00 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The nearest one is 4FGL J0100.3+0745 within the 90% uncertainty region of the event, 1.68 deg away from the best-fit event position (GCN 33204, 33212). We observed the BL Lac object 4FGL J0100.3+0745 and the best-fit position of IceCube-230122A with BOOTES-2/TELMA robotic telescope.The magnitudes were calculated using bright stars in the same frame and the SDSS DR16 catalogue as reference. We did not detect any optical source within the best-fit position, and also the optical counterpart of the 4FGL J0100.3+0745. The upper limits of magnitudes (without being corrected for Galactic extinction) are given as follows. Sources | Tmid-T0 (day) | UT (start) | Upper Limit (error) | Exposure Time | Filter -------------------------------------------------------------------------------------------------------------- Best-fit position | 0.764 | 23-01-22 22:10:44.8 | 18.79 (0.22) | 2*300s (co-added) | Clear 4FGL J0100.3+0745 | 0.699 | 23-01-22 20:36:22.3 | 19.51 (0.03) | 8*300s (co-added) | Clear --------------------------------------------------------------------------------------------------------------- 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 BOOTES-2/TELMA robotic telescope at IHSM La Mayora (UMA-CSIC) in Algarrobo Costa (Malaga, Spain). We acknowledge the support of these staffs from the BOOTES telescope networks.