TITLE: GCN CIRCULAR NUMBER: 42248 SUBJECT: GRB 251013C: J band observations by SYSU 80cm infrared telescope DATE: 25/10/14 07:17:23 GMT FROM: zhanghr33@mail2.sysu.edu.cn Hao-Ran Zhang, Chen Chun, Duo-Le Cao, Zhong-Nan Dong, Wei-Sen Huang, Jin-Ji Li, Jia-Qi Lin, Pu Lin, Yan Yu, Hao-Nan Yang, P H Thomas Tam, Rong-Feng Shen, Bin Ma (Sun Yat-sen University) report on behalf of the SYSU 80cm infrared telescope team: We observed the field of GRB 251013C detected by SVOM (N. A. Rakotondrainibe et al., GCN 42222) and Fermi (Fermi GBM Team, GCN 42221), using the Sun Yat-sen University 80cm infrared telescope with 20 s exposures in J band. The calculated position is R.A. = 345.8301 deg, Dec = -0.2207deg J2000, from SVOM observation. Our observations began at 2025-10-13 18:03:42 UTC, 0.41 hours after the SVOM trigger. We clearly detect an infrared counterpart at the position of the optical afterglow (J. T. Palmerio et al., GCN 42223; I. Perez-Garcia et al., GCN 42225; R. Konno et al., GCN 42226; L. A. Martin-Carrillo et al., GCN 42227; Gianluca Masi, GCN 42228; J. T. Palmerio et al., GCN 42229; A. S. Moskvitin et al., GCN 42230; B. P. Gompertz et al., GCN 42231; V.Lipunov et al., GCN 42235; P. Garnavich, GCN 42240; Alan M. Watson et al., GCN 42241; Diego López-Cámara et al., GCN 42242). The earliest detection is confirmed at 2025-10-13 18:03:42UTC (T – T0 = 0.41 h) with J mag: 13.49+/-0.14 (Vega system). Preliminary photometry shows a rise of ~0.4mag at 18:26:00UTC (T – T0 = 0.78 h), followed by a rapid decay. The photometric calibration was performed using nearby stars from the 2MASS catalog. The photometric accuracy is limited due to the cloudy weather. The SYSU 80cm infrared telescope is operated and managed by the Department of Astronomy, Sun Yat-sen University. View this GCN Circular online at https://gcn.nasa.gov/circulars/42248. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...