[vsnet-grb-info 27526] GRB 210307A: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29629
SUBJECT: GRB 210307A: Swift/UVOT Upper Limits 
DATE:    21/03/08 23:38:27 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18 at psu.edu>

M. H. Siegel (PSU) and E. Ambrosi (INAF-IASFPA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210307A
100 s after the BAT trigger (Ambrosi et al., GCN Circ. 29610).
No optical afterglow consistent with the XRT position
(Ambrosi et al. GCN Circ. 29610)
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           100          250          147         >20.9
u_FC               313          562          246         >20.6
white              100          786          186         >21.1
v                  642          836           39         >19.3
b                  568          761           39         >19.9
u                  313          736          265         >20.6
w1                 692          711           19         >19.6
m2                 667          687           19         >18.7
w2                 618          812           39         >19.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.138 in the direction of the burst
(Schlegel et al. 1998).