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GCN Circular 30767

GRB 210901A: Swift/UVOT Upper Limits
2021-09-05T00:48:10Z (3 years ago)
Mike Siegel at PSU/Swift MOC <>
M. H. Siegel (PSU) 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 210901A
158 s after the BAT trigger (Laha et al., GCN Circ. 30746).
No optical afterglow consistent with the XRT position
(Osborne et al. GCN Circ. 30749)
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           158          308          147         >20.9
u_FC               316          566          246         >19.6
white              158          974          289         >20.9
v                  646          839           39         >17.8
b                  572          764           39         >18.8
u                  316          740          265         >19.8
w1                 695          715           19         >17.8

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.200 in the direction of the burst
(Schlegel et al. 1998).
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