[vsnet-grb-info 21069] GRB 180821A: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23167
SUBJECT: GRB 180821A: Swift/UVOT Upper Limits
DATE:    18/08/22 16:24:33 GMT
FROM:    Frank Marshall at Swift/UVOT  <marshall at milkyway.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and A. Tohuvavohu (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180821A
219 s after the BAT trigger (Tohuvavohu et al., GCN Circ. 23158).
No optical afterglow consistent with the enhanced XRT position
(Evans et al. GCN Circ. 23162) 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           219          369          147         >21.0
white              219          495          167         >21.1
v                  526          546           19         >17.7
v                 4604         6039          393         >20.0
b                  451          471           19         >19.3
b                 3988         5624          393         >21.3
u                  426          446           19         >18.6
u                 3783         5418          393         >20.5
w1                 402          421           19         >19.3
w1                5015        15906          241         >20.5
m2                4808        10398          812         >20.5
w2                4399         6034          393         >20.3

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).