TITLE: GCN CIRCULAR NUMBER: 42972 SUBJECT: GRB 251129A / EP251129a: SVOM/VT optical color bluer DATE: 25/12/03 15:51:33 GMT FROM: Huali Li at at NAOC, SVOM <lhl@nao.cas.cn> L. P. Xin, H. L. Li, Y. L. Qiu, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed further ToO observations for GRB 251129A / EP251129a triggered by SVOM/ECLAIRs (sb25112901, Tan et al., GCN 42877, GCN 42879) and Einstein Probe (Wu et al., GCN 42884). The observations showed the color of the afterglow (Evans, GCN 42888; Angulo et al., GCN 42880; Watson, GCN 42883; Wu et al., GCN 42882; Masi, GCN 42885; Li et al., GCN 42887; Page et al., GCN 42891; Lipunov et al., GCN 42892; Moskvitin et al., GCN 42897; Guziy et al., GCN 42899; Sanchez-Ramirez et al., GCN 42900; Jiang et al., GCN 42902; Yaqup et al., GCN 42942; Kuin et al., GCN 42959) was changed from VT_B-VT_R~0.30+/-0.03 mag at 0.5 hours to VT_B-VT_R~0+/-0.05 mag at around 4 to 50 hours post burst. The latest measurements are 21.8+/-0.1 mag in both channels at the mid time of 49.83 hours post burst with the exposure time of 47*70 sec. Our photometry was in AB magnitude and not corrected for Galactic extinction. More follow-up observations are encouraged. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/42972. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...