GCN Circular 6648
Subject
Swift/UVOT Observations of GRB070721A
Event
Date
2007-07-21T18:56:56Z (19 years ago)
From
Patricia Schady at MSSL/Swift <ps@mssl.ucl.ac.uk>
P. Schady (MSSL-UCL) and H. Ziaeepour (MSSL-UCL) report on behalf of the
Swift/UVOT team:
The Swift/UVOT observed the field of GRB 070721A starting 69 s after the
BAT trigger (Ziaeepour et al. GCN Circ.6639). We do not find any source,
in any of the UVOT observations inside the refined XRT error circle (Evans
et al., GCN Circ.6644). However, we note that there is an 18th mag star 4
arcseconds from the XRT refined position.
The 3-sigma upper limits for detecting a source inside the XRT error
circle are:
Filter T_mid(s) Exp(s) Mag (3-sig upper limit)
=================================================
White 1088 156 > 21.7
V 1194 453 > 20.9
B 1509 97 > 19.5
U 1359 117 > 20.0
UVW1 1334 117 > 19.6
UVM2 1309 117 > 19.2
UVW2 1530 97 > 19.4
where T_mid is the weighted mid time of the coadded exposure. The values
quoted above are not corrected for the expected Galactic extinction
corresponding to a reddening of E(B-V) = 0.01 mag in the direction of the
burst (Schlegel et al. 1998).