GCN Circular 23138

GRB 180812A: Swift/UVOT Detection

S. J. LaPorte (PSU) and A. Y. Lien (GSFC/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180812A
112 s after the BAT trigger (Lien et al., GCN Circ. 23129
Not found
 
 
).
A fading source consistent with the XRT position
(Goad et al. GCN Circ. 23131
Not found
 
 
)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  16:23:20.45 =  245.83522 (deg.)
    Dec (J2000) = 74:39:52.9 =  74.66471 (deg.)
with an estimated uncertainty of 0.50 arc sec. (radius, 90% confidence),
consistent with detections reported by BOOTES-5/JGT (Carrasco et al. GCN
Circ. 23130
Not found
 
 
) and COATLI (Watson et al. GCN Circ. 23132
Not found
 
 
).

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              140          289          431         19.81 +/- 0.17
white             1551         2092           77        >20.85
v                  600         6610          372        >18.9
b                  526         5994          352        >20.0
u                  270         5789          598        >19.8
w1                 650         6857          211        >19.5
m2                6616         6815          197        >20.2
w2                6206         6406          197        >20.2

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.04 in the direction of the burst
(Schlegel et al. 1998).