[vsnet-grb-info 27592] GRB 210318B: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29695
SUBJECT: GRB 210318B: Swift/UVOT Upper Limits
DATE:    21/03/23 03:30:27 GMT
FROM:    Sam LaPorte at PSU  <sjl5346 at psu.edu>

 GRB 210318B: Swift/UVOT Upper Limits

M. H. Siegel (PSU) and E. Troja (NASA/GSFC, UMCP)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210318B
70 s after the BAT trigger (Troja et al., GCN Circ. 29663).
No optical afterglow consistent with the XRT position
(Troja et al. GCN Circular 29663)
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            70          219          147         >20.0
u_FC               282          532          246         >20.1
white               70         1357          373         >20.9
v                  612         1406           97         >18.2
b                  538         1500           92         >19.1
u                  282         1479          324         >20.1
w1                 661         1455           97         >18.8
m2                1066         1430           58         >19.3
w2                 588         1382           97         >19.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 1.718 in the direction of the burst
(Schlegel et al. 1998).