TITLE:   GCN CIRCULAR
NUMBER:  9552
SUBJECT: GRB 090621B: Swift/UVOT Upper Limits
DATE:    09/06/22 13:45:39 GMT
FROM:    Peter Curran at MSSL  <pac@mssl.ucl.ac.uk>

P.A. Curran (MSSL-UCL) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 090621B
76s after the BAT trigger (Curran et al., GCN 9545). No optical
afterglow consistent with the refined XRT position (Beardmore et al.,
GCN 9550) or the optical source observed by Levan et al. (GCN  9547) is
detected in the UVOT exposures.

Preliminary 3-sigma upper limits using the UVOT photometric system
(Poole et al. 2008, MNRAS, 383, 627) for the first exposures are:

Filter	T_start(s) T_stop(s)  Exp(s)  Mag
wh      76         18173      1221    >22.29
v       618        10774      1142    >20.67
b       544        23952      1986    >21.88
u       289        29731      2675    >21.77
uw1     668        29017      2882    >21.63
um2     643        28110      2006    >21.32
uw2     594        6589       432     >20.50

The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.44 in the direction of the burst
(Schlegel et al. 1998).