[vsnet-grb-info 18483] GRB 160917A: Swift/UVOT Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19931
SUBJECT: GRB 160917A: Swift/UVOT Detection
DATE:    16/09/17 23:54:38 GMT
FROM:    Paul Kuin at MSSL  <npkuin at gmail.com>

N. P. M. Kuin (UCL-MSSL) and J. L. Racusin (NASA/GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160917A
100 s after the BAT trigger (Racusin et al., GCN Circ. 19926). The
refined XRT position (Evans et al. GCN Circ. 19927) is close to a
bright star. However, a faint GRB candidate has been found at an
offset of 6.5 arcsec to the south east from the bright star in the
u exposures.
The UVOT candidate position is: RA, Dec = 295.66687, 46.40368 (J2000)
which is :
RA = 19:42:40.049
Dec = +46:24:13.25
with an estimated accuracy of 1.5 arcsec.

Preliminary detections using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures
are:

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white              100          224          123          >21.01
b                 4222         4422          100          >20.64
u                 4017         5545          146           20.47 +- 0.36
v                 3402         5038          200          >19.77
uvw1              3812         5448          200          >20.16
uvm2              3606         5242          100          >19.97
uvw2              4633         4833          200          >19.70

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.16 in the direction of the burst
(Schlegel et al. 1998).