[vsnet-grb-info 20379] GRB 180311A: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22475
SUBJECT: GRB 180311A: Swift/UVOT Upper Limits
DATE:    18/03/12 16:42:41 GMT
FROM:    Frank Marshall at Swift/UVOT  <marshall at 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. 22468).
No optical afterglow consistent with the enhanced XRT position
(Goad et al. GCN Circ. 22470)
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).