GCN Circular 26002

N. P. M. Kuin (UCL-MSSL) and Laha (GSFC/UMBC/CRESST)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 191011A
78 s after the BAT trigger (Laha et al., GCN Circ. 25988
Not found
 
 
).  A source
consistent with the XRT position (Evans et al. GCN Circ. 25995
Not found
 
 
)
is detected in the initial UVOT exposures. This GRB was also detected
by Fermi/GBM (GCN Circ. 25987
Not found
 
 
,26000
Not found
 
 
) and Insight-HXMT-HE(Yi et al, GCN
Cir. 25997). A redshift was reported using the VLT/Xshooter (Kahn et al,
GCN Circ.25991
Not found
 
 
), while the optical afterglow was reported from Master
(Lipunov et al, GCN Circ. 25990
Not found
 
 
; GROND (Nicuesa Guelbenzu et al.,
GCN Circ. 25992
Not found
 
 
).

The preliminary UVOT position is:
    RA  (J2000) =  02:58:54.79 =  44.72829 (deg.)
    Dec (J2000) = -27:50:43.4  = -27.84540 (deg.)
with an estimated uncertainty of 0.73 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               78          228          147         20.27 +/- 0.16
v                  620        11672         1211        >20.2
b                  545         7080          510         21.03 +/- 0.27
u                  290         6875          697         20.86 +/- 0.27
w1                 670         6670          510        >20.3
m2                1073        12198          767        >21.1
w2                1024         7491          432        >20.9

The afterglow is seen to be nearly constant in the white filter until
about 1000s, whereafter a decay is observed.  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).