[vsnet-grb-info 27156] GRB 210104B: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29259
SUBJECT: GRB 210104B: Swift/UVOT Upper Limits
DATE:    21/01/05 14:18:56 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld at ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and S. L. Laha (GSFC/UMBC/CRESST) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210104B 84 s after the BAT trigger 
(Laha et al., GCN Circ. 29243).
No optical afterglow consistent with the XRT position (Evans et al. GCN Circ. 29253) 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            84          234          147         >20.5
u_FC               296          546          246         >19.8
white               84          753          172         >20.7
v                  625          645           19         >17.6
b                  551          743           39         >19.1
u                  296          719          265         >19.9

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of 
E(B-V) = 0.79 in the direction of the burst (Schlegel et al. 1998).