[vsnet-grb-info 17876] GRB 160417A: Swift/UVOT Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19322
SUBJECT: GRB 160417A: Swift/UVOT Detection
DATE:    16/04/17 18:40:24 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld at ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and P. D'Avanzo (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160417A
136 s after the BAT trigger (D'Avanzo et al., GCN Circ. 19316).
The source reported for the UVOT in the initial GCN and also by Zheng 
and Filippenko (GCN Circ. 19317) is found to be fading.

The preliminary UVOT position is:
     RA  (J2000) =  08:01:01.64 = 120.25685 (deg.)
     Dec (J2000) = +07:39:46.4  =   7.66289 (deg.)
with an estimated uncertainty of 0.46 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits 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              136          285          147         18.92 ± 0.07
white              870         1020          147         19.14 0.10
v                  623         1070           58         18.54 ± 0.31
b                  549         1169           58         19.07 ± 0.21
u                  294          543          246         18.08 ± 0.08
w1                 672         1280           64        >18.9
m2                 647         1268           78        >19.1
w2                 599         1220           78        >18.8

The magnitudes in the table 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).