GCN Circular 13235
Subject
GRB 120404A: optical observations
Date
2012-04-07T22:40:19Z (12 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
A. Volnova (SAI MSU), D. Varda (ISON), E. Sinyakov (ISON), E. Litvinenko
(UBAI), V. Kouprianov (GAO), I. Molotov (KIAM), A. Pozanenko (IKI) on behalf
of larger GRB follow up collaboration report:
We observed the field of the Swift GRB 120404A (Stratta et al., GCN 13208)
with ORI-25 (0.25-m) telescope of ISON-Blagoveschensk observatory between
Apr. 04 (UT) 13:06:10 - 14:43:45 and ORI-40 (0.4-m) telescope of ISON-Kitab
observatory between Apr. 04 (UT) 17:13:02 - 18:16:58. Several unfiltered
images were taken in both observatories. We detected optical afterglow
(Stratta et al., GCN 13208; Guidorzi et al., GCN 13209) in combined image
(see below). Coordinates of the OT are (J2000) 15:40:02.17, +12:53:06.5
with unceraininty of 0.75" on both coordinates which is compatible with
coordinates reported by UVOT team (Stratta et al., GCN 13208). A photometry
is based on nearby USNO-B1.0 stars (R2 magnitude):
t_start, t-t0 (mid), filter exp., OT, UL
(UT) d s
13:06:10 0.01529 none 12x25 n/d 16.5
13:21:11 0.03700 none 38x25 17.35 +/- 0.25 17.5
14:08:43 0.06611 none 29x25 n/d 17.9
17:13:02 0.20378 none 60x60 n/d 18.9
Based on initially non-detection of the OT we can confirm the brightening of
the afterglow (Breeveld et al., GCN 13226; Tristram et al., GCN 13228;
Gorbovskoy et al., GCN 13230) with a peak between (UT) 13:21 and 14:06
(i.e. ~ 50 min after burst trigger).