TITLE: GCN CIRCULAR NUMBER: 42078 SUBJECT: GRB 251002A: J band observations by SYSU 80cm infrared telescope DATE: 25/10/03 07:45:53 GMT FROM: caodle@mail2.sysu.edu.cn Dou-Le Cao, Jia-Qi Lin, Chen Chun, Zhong-Nan Dong, Wei-Sen Huang, Jin-Ji Li, Pu Lin, Yan Yu, Hao-Nan Yang, Hao-Ran Zhang, 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 GRB251002A detected by SVOM/ECLAIRs (A. Saccardi et al., GCN 42060), using the Sun Yat-sen University 80cm infrared telescope with 20s exposures in J band. The calculated position is R.A. = 13.9082 deg, DEC = -5.5671 deg J2000, from SVOM/VT observation. Our observations began at 2025-10-2 20:55:00 UTC, 0.62 hours after the SVOM trigger. We detected an infrared counterpart at the position of the optical afterglow (J. T. Palmerio et al., GCN 42061; D. Turpin et al., GCN 42062; Martin Jelinek et al., GCN 42063; L. Juliá-Maroto et al., GCN 42064; A. S. Moskvitin et al., GCN 42065; I. Perez-Garcia et al., GCN 42066; V.Senik et al., GCN 42067) in the stacked images. The preliminary photometric magnitudes in J band are below: Start Time (UTC) |Band | Exp | Mag (Vega) ------------------------|-------|---------|------------------ 2025/10/2 20:55:00 | J | 300s | 17.03+/-0.24 2025/10/2 21:00:00 | J | 300s | 17.19+/-0.14 2025/10/2 21:05:00 | J | 300s | 17.64+/-0.20 2025/10/2 21:10:00 | J | 300s | 17.44+/-0.15 2025/10/2 21:15:00 | J | 300s | 17.74+/-0.19 2025/10/2 21:20:00 | J | 900s | 17.65+/-0.16 2025/10/2 21:35:00 | J | 2100s | 18.27+/-0.15 The photometric calibration was performed using nearby stars from the 2MASS catalog and the magnitudes are not corrected for Galactic extinction. 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/42078. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...