GCN Circular 13973

Subject
GRB 121117A: Swift/UVOT Observations
Event
Date
2012-11-18T12:41:31Z (13 years ago)
From
Samantha Oates at MSSL <sro@mssl.ucl.ac.uk>
S. R. Oates (MSSL-UCL) and J. R. Cummings (NASA/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 121117A
s after the BAT trigger (Cummings et al., GCN Circ. 13967Loading...
 
 ).
We find an optical afterglow consistent with the XRT position
(Beardmore et al. GCN Circ. 13972Loading...
 
 ) in the initial UVOT white exposure.
The refined UVOT position is (RA,DEC) = 31.61063, 7.41956 (J2000), 
which is equivalent to:

RA (J2000)  =  02:06:26.56
Dec (J2000) =  +07:25:10.5

with an estimated uncertainty of 0.6 arcsec (radius, 90% confidence).

Preliminary magnitudes and 3-sigma upper limits using the UVOT photometric 
system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial 
exposures are:

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

white (FC)        57            205          146         19.17 +/- 0.10
white             4606        10267         1150         >21.9
v                 3580        11882         1077         >20.3
b                 4400         6037          393         >20.6
u                 4195         5831          393         >20.3
w1                3990         5627          393         >20.3
m2                3785         5421          393         >20.2
w2                4811        11174         1082         >21.3

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.06 in the direction of the burst
(Schlegel et al. 1998).