[vsnet-grb-info 17899] GRB 160422A: Swift/UVOT Afterglow Confirmation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19346
SUBJECT: GRB 160422A: Swift/UVOT Afterglow Confirmation
DATE:    16/04/26 02:00:23 GMT
FROM:    Frank Marshall at GSFC  <femarsha at khamseen.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160422A
32624 s after the LAT trigger (Yassine et al., GCN Circ. 19329).
The optical afterglow candidate (Marshall, GCN Circ. 19333)
has faded in a later observation in the same filter.
Its positional consistency with the  XRT source
(Maselli et al. GCN Circ. 19334) and its fadiing
behavior confirm that it is the optical afterglow of GRB 160422A.

The preliminary UVOT position is:
    RA  (J2000) =  02:48:22.78 =  42.09493 (deg.)
    Dec (J2000) = -57:52:30.4  = -57.87512 (deg.)
with an estimated uncertainty of 0.45 arc sec. (radius, 90% confidence).

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            33427        34064          627         19.50 � 0.05
white            44903        44701          785         19.91 � 0.06
v                39970        45820          320         19.29 � 0.23
u                32624        33420          783         19.09 � 0.10

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).