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GCN Circular 30729

Subject
GRB 210826A: Swift/UVOT Upper Limits
Date
2021-08-27T15:38:05Z (3 years ago)
From
Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>
A. A. Breeveld (UCL-MSSL) and T. Sbarrato (INAF-IASFPA) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210826A 36747 s after the LAT trigger 
(Ohno et al., GCN Circ. 30721). No new optical source consistent with the any of the 8 candidate XRT 
positions (D'Ai et al., GCN Circ. 30725) 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 initial exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

v                36747        49716         4869         >20.9

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of 
E(B-V) = 0.032 in the direction of the burst (Schlegel et al. 1998).
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