TITLE: GCN CIRCULAR NUMBER: 39102 SUBJECT: GRB 250129A: continued KAIT observations indicating steep decay after 28.5h DATE: 25/01/30 22:40:51 GMT FROM: Weikang Zheng at UC Berkeley <weikang@berkeley.edu> WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, continued observing the afterglow of the GRB 250129A (Francile et al., GCN 39065; Beardmore et al., GCN 39066; Schneider et al., GCN 39071; Belkin et al., GCN 39072; Izzo et al., GCN 39073; Izzo & Malesani, GCN 39074; Gosh et al., GCN 39077; Schneider et al., GCN 39078; Brivio et al., GCN 39079; Siegel et al., GCN 39085; Zheng et al. GCN 39090; Schlekat et al., GCN 39091; Antier et al., 39096; Odeh et al., GCN 39097; Ferro et al., GCN 39098; Bochenek et al., GCN 39099; Malesani et al., GCN 39100; Romanov, GCN 39101) in the clear (roughly R) band. Observation started at ~28.5h after the burst and lasted for ~5.0h. The OT was still clearly detected in every individual image. Our photometry results show that the OT was in a single power-law decay phase, decayed from ~18.6 mag (~28.5h) to ~19.5 mag (~33.5h) with a decay index of ~4.1, much steeper compared to the value of ~0.85 reported by Bochenek et al. (GCN 39099). This indicating the OT is likely in a post jet-break phase. View this GCN Circular online at https://gcn.nasa.gov/circulars/39102. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...