GCN Circular 42083
Subject
GRB 251001B: AbAO optical upper limit
Event
Date
2025-10-03T09:51:25Z (6 days ago)
From
Nicolai Pankov at HSE, IKI RAS <colinsergesen@gmail.com>
Via
Web form
N. Pankov (HSE, IKI), A. Pozanenko (IKI), R. Ya. Inasaridze (AbAO) report on behalf of IKI-GRB-FuN:
We performed optical observations of the field of GRB 251001B detected by Fermi/GBM (The Fermi GBM team et. al, GCN 42038), and Swift/BAT (Beardmore et. al, GCN 42039) with the AS-32 0.7m telescope of the Abastumani Observatory (AbAO). The R-filter observations began on 2025-10-01 22:37 UT, i.e. ~0.35 days since trigger and consisted of 55x30 s exposures. The optical source at z = 2.162 (Sanchez-Ramirez et. al, GCN 42053) found by GOTO (Gompertz et. al, GCN 42040) and also observed by (An et. al, GCN 42041; Strausbaugh & Cucchiara, GCN 42043; O'Neill et. al, GCN 42046; de Ugarte Postigo et. al, GCN 42050; Ma et. al, GCN 42051; Sanchez-Ramirez et. al, GCN 42053; Schneider et. al, GCN 42054; Breeveld et. al, GCN 42055) is not detected in the co-add image of 51x30 s. Preliminary photometry and observation details are presented below:
Date UT start t-T0 Exp. Filter OT Err. UL
(mid, days) (s) (3sigma)
2025-10-01 22:37:48 0.35641 51x30 R n/d n/d 19.9
The photometry was calibrated using nearby stars from USNO-B1.0 (R2 magnitudes) and not corrected for the Galactic extinction.
Ref. stars
USNO-B1.0
RA Dec R2
42.63445 -23.02161 14.13
42.77496 -23.05166 13.47