GCN Circular 8990

P.Schady (MSSL-UCL) S.T. Holland (CRESST/GSFC/USRA) and J. Mao (INAF-OAB) 
report on behalf of the Swift/UVOT team:

The Swift/UVOT began observing the field of GRB 0903013 once it came out 
of Moon constraint, 27ks after the BAT trigger (Mao et al., GCN Circ. 
8980
Not found
 
 
). There is no afterglow detection in any of the b, u or uvw1 UVOT 
filter observations taken at the optical afterglow position reported by 
Chornock et al. (GCN 8979
Not found
 
 
), although by coadding all filters into a single 
exposure, a source is marginally detected at the 2-sigma level.

The 3-sigma upper limits for GRB090313 within each UVOT filter are as 
follows:

Filter      T_mid(hrs)   Exp(s)  3-sig Mag UL
u             7.98        223      > 20.81
b             7.82        885      > 21.36
uvw1          7.57        886      > 21.32

where Tmid is the weighted mean time of the observations. The values 
quoted above are not corrected for the Galactic extinction due to the 
reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 
1998).