GCN Circular 21388

GRB 170728B: Swift/UVOT Upper Limits

S. J. Laporte (PSU) and S. B. Cenko (GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 170728B
473 s after the BAT trigger (Cenko et al., GCN Circ. 21371
Not found
 
 
).
No optical afterglow consistent with the optical position
(D'Avanzo et al. GCN Circ. 21373
Not found
 
 
)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

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

white_FC           473          623          147         >19.8
white              473         7867          908         >20.8
v                  630         8278          627         >19.6
b                  728        14417         1117         >21.3
u                  703        13868         1276         >21.2
w1                 679        19251         2000         >21.6
m2                6847        18681         1279         >22.1
w2                6437         8073          393         >21.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.03 in the direction of the burst
(Schlegel et al. 1998).