GCN Circular 22475

Subject

GRB 180311A: Swift/UVOT Upper Limits

Event

Date

2018-03-12T16:42:41Z (8 years ago)

From

Frank Marshall at Swift/UVOT <marshall@milkyway.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and K. L. Page (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180311A
280 s after the BAT trigger (Page et al., GCN Circ. 22468Loading...
 
 ).
No optical afterglow consistent with the enhanced XRT position
(Goad et al. GCN Circ. 22470Loading...
 
 )
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           280          430          147         >20.3
white              280         6742          589         >21.2
v                  437         7155          333         >19.4
b                  536         8600          488         >20.9
u                  511         7770          561         >20.5
w1                 486         7565          330         >20.2
m2                7160         7360          197         >20.3
w2                1187         6950          255         >20.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.01 in the direction of the burst
(Schlegel et al. 1998).