GCN Circular 6392
Subject
GRB070508: Swift/UVOT Observations
Event
Date
2007-05-08T22:24:16Z (19 years ago)
From
Frank Marshall at GSFC <marshall@milkyway.gsfc.nasa.gov>
F.E. Marshall (NASA/GSFC) and D. Grupe (PSU) report on behalf of the
Swift/UVOT team:
UVOT began observing GRB 070508 68s after the BAT trigger
(Grupe et al., GCN Circ. 6383). A fading afterglow is
detected in the White and V filters, while no afterglow is seen
in the B, U, or UV filters. We use the first white exposure
to obtain an improved position of
RA(J2000) = 20h 51m 11.68s Dec(J2000) = -78d 23' 05.0"
with a 90% confidence statistical uncertainty in each axis of 0.5".
There is also a 1-sigma systematic uncertainty in the UVOT
aspect solution of about 0.3". This revised position is 0.6" from
the initial UVOT position reported by Grupe et al. and 2.3" from the
position for the I-band object reported by Berger and Burgasser
(GCN Circ. 6386).
Thoene et al. (GCN Circ. 6389) have suggested a redshift of
greater than 3.5 based on their detections in the I and R bands
and lack of detection in V band. The UVOT detection in the V filter
indicates a redshift of less than 5.
Photometry results with statistical errors are given below
for the 7 UVOT filters. The start and stop times (in seconds)
are referenced to the trigger time, and the total exposure
time (Exp.) is given in seconds.
T_start T_stop Exp. Mag
White 86 185 98 19.8+/-0.12 (1-sigma)
V 192 571 393 19.7+/-0.22 (1-sigma)
B 669 1946 86 >19.6 (90% confidence)
U 644 1933 117 >18.4 (90% confidence)
UVW1 620 7389 283 >18.2 (90% confidence)
UWM2 1705 7215 236 >17.8 (90% confidence)
UVW2 698 6806 294 >18.6 (90% confidence)
No correction has been made for the expected Galactic reddening of
E(B-V)=0.14