GCN Circular 39102
Subject
GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
Event
Date
2025-01-30T22:40:51Z (9 months ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
Via
email
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.