GCN Circular 9774
Subject
GRB090812: Swift/UVOT observations
Event
Date
2009-08-12T13:52:31Z (17 years ago)
From
Patricia Schady at MSSL/Swift <ps@mssl.ucl.ac.uk>
P. Schady (MSSL-UCL) and M. Stamatikos (NASA/ORAU) report on behalf of the
Swift UVOT team:
The Swift/UVOT began settled observations of the field of GRB 090812 86s
after the BAT trigger (Stamatikos et al., GCN Circ. 9768). An
uncatalogued, fading source is detected in the UVOT white, v, b and u band
filters at the position reported in Stamatikos et al. (GCN Circ. 9768),
consistent with the refined XRT error circle (Goad et al., GCN Circ.
9772). The detection of the afterglow in the white, v, b and u filters is
consistent with the spectroscopic redshift of z=2.452 reported by Ugarte
Postigo et al. (GCN Circ. 9771). Early time UVOT obserations indicate a
decay rate of alpha~1.5.
The magnitudes and 3-sigma upper limits for the UVOT observations of GRB
090812 in each filter are as follows:
Filter T_start(s) T_stop(s) Exp(s) Mag/3-sig UL
white 86 235 146 17.35+/-0.03
v 628 647 19 18.17+/-0.41
b 554 573 19 18.62+/-0.28
u 299 548 246 18.65+/-0.11
uvw1 677 1124 58 > 19.20
uvm2 652 1099 58 > 18.72
uvw2 603 1050 58 > 19.13
The values quoted above are not corrected for the Galactic extinction due
to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel
et al. 1998). The photometry is on the UVOT photometric system described
in Poole et al. (2008, MNRAS, 383, 627).