TITLE: GCN CIRCULAR NUMBER: 31529 SUBJECT: IceCube-211208A: the optical observation of the candidate PKS0735+178 DATE: 22/01/29 06:24:16 GMT FROM: Jirong Mao at Yunnan Obs D. R. Xiong, J. Mao, Y. Xin，D. H. Yan, J.-M. Bai (YNAO), and Y. L. Chang, W. Li, D. L. Xu (TDLI) report: We follow the IceCube-211208A alert (GCN circ. 31191), and we observe the BL Lac object PKS0735+178, which might be the source candidate of IceCube-211208A. We have performed the optical monitor in each night since 11, Dec. 2021. The 2.4-meter telescope and the BOOTES-4 telescope located at Gao-Mei-Gu (GMG) station of Yunnan Observatories are utilized for the multi-band photometry. We have obtained the very preliminary results. As an example, the magnitude of r=14.69 was measured from the observation in 11, Dec. 2021, and the the magnitude of r=15.60 was measured from the observation in 14, Jan. 2022. We note that the magnitude of r=15.50 is provided for this source by the Sloan Digital Sky Survey. The multi-band photometric monitor is ongoing. We are working on the careful data reduction. The long-term multi-wavelength observation for this target is encouraged. We acknowledge the support of the staff from the Lijiang GMG 2.4-m telescope and the BOOTES telescopes (A. J. Castro-Tirado and E. Fernandez- Garcia et al.).