GCN Circular 21184
Subject
GRB 170531A: Swift/UVOT Upper Limits
Event
Date
2017-06-01T16:02:44Z (9 years ago)
From
Mike Siegel at PSU/Swift MOC <siegel@swift.psu.edu>
M. H. Siegel (PSU) and P. A. Evans (U. Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 170531A
3523 s after the BAT trigger (Evans et al., GCN Circ. 21170).
No optical afterglow consistent with the XRT position
(Melandri et al., GCN Circ. 21180) is detected in the initial UVOT exposures.
We note that the XRT position is 3.5� away from a known USNO-B1 source, which
we detect. There is no indication of a second source within the error circle.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 3523 3673 147 >18.1
white 3523 4292 344 >18.2
v 4502 4702 197 >17.5
b 3887 4087 197 >18.2
u 3682 3881 197 >18.0
w2 4298 4497 197 >19.4
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.09 in the direction of the burst
(Schlegel et al. 1998).