GCN Circular 10041
Subject
GRB091018: Swift/UVOT observations
Date
2009-10-19T04:12:08Z (15 years ago)
From
Wayne Landsman at GSFC/SSAI <wayne.b.landsman@nasa.gov>
W.B. Landsman (NASA/GSFC) and M. Stamatikos (OSU/NASA/GSFC) report on
behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 091018
69s after the BAT trigger (Stamatikos et al., GCN 10034). The
afterglow is well-detected in all seven UVOT filters at the position
reported by Stamatikos et al. The initial magnitudes are as follows:
Filter T_start(s) Exp(s) Mag
white 69 147 14.57 � 0.012
white 860 147 16.48 � 0.018
u 281 246 15.07 � 0.017
u 6911 197 18.04 � 0.08
v 610 19 16.4 � 0.14
b 536 19 16.4 � 0.08
uvw1 660 20 15.9 � 0.12
uvm2 635 20 15.7 � 0.16
uvw2 586 20 16.1 � 0.15
The detection in the uvw2 filter indicates a redshift less than z = 1.1,
consistent with the value of z= 0.971 reported by the Magellan group (
Chen et al., GCN 10038).
The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.029 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).