GCN Circular 13226
Subject
GRB 120404A: Swift/UVOT Detection
Date
2012-04-05T11:44:46Z (12 years ago)
From
Alice Breeveld at MSSL-UCL <aab@mssl.ucl.ac.uk>
A. A. Breeveld (MSSL-UCL) and G. Stratta (ASDC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 120404A
139 s after the BAT trigger (Stratta et al., GCN Circ. 13208).
A source at the UVOT position given in Stratta et al., GCN Circ. 13208,
and consistent with the enhanced XRT position (Osborne et al., GCN Circ.
13218), is detected in the initial UVOT exposures. The source is only
seen in the optical filters and rises initially and then fades. The fact
that the source is not detected in the UV filters is consistent with the
redshift of z=2.876 reported by Cucchiara et al., GCN Circ. 13217.
Preliminary detections and 3-sigma upper limits using the UVOT
photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for
the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 139 288 147 19.43 � 0.12
v 4734 4934 197 17.69 � 0.10
b 606 1178 58 19.22 � 0.28
u 351 1327 304 19.90 � 0.19
w1 729 6779 452 >20.3
m2 704 6574 432 >21.5
w2 656 11408 1179 >22.1
The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.05 in the direction of the
burst (Schlegel et al. 1998).