[vsnet-grb-info 7926] GRB 090531B: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9469
SUBJECT: GRB 090531B: Swift/UVOT Upper Limits
DATE:    09/06/01 10:06:42 GMT
FROM:    Patricia Schady at MSSL/Swift  <ps at mssl.ucl.ac.uk>

P. Schady (MSSL-UCL) and J. R. Cummings (NASA/UMBC) report on behalf of 
the Swift/UVOT team:

The Swift/UVOT observed the field of GRB 090531B starting 3924 s after the 
BAT trigger (Cummings et al., GCN Circ. 9461), once the GRB came out of 
Earth limb observing constraint. No optical afterglow is detected in any 
of the UVOT exposures at the position of the X-ray afterglow (Sbarufatti 
et al., GCN Circ. 9463), with the following three-sigma upper limits:

Filter  T_mid(s)  Exp(s)   3-sig Mag UL

white    3934      74      > 20.52
v        4105      98      > 19.08
b        4926      98      > 20.06
u        4721      98      > 19.74
uvw1     4515      98      > 19.65
uvm2     4310      98      > 19.32
uvw2     5336      98      > 19.61

The values quoted above are not corrected for the large Galactic 
extinction due to the reddening of E(B-V)=1.12 in the direction of the 
burst (Schlegel et al. 1998). The photometry is on the UVOT photometric 
system described in Poole et al. (2008, MNRAS, 383, 627).