TITLE:   GCN CIRCULAR
NUMBER:  8386
SUBJECT: GRB 081016B: Swift/UVOT Upper Limits
DATE:    08/10/17 15:47:39 GMT
FROM:    Wayne Landsman at GSFC/SSAI  <wayne.b.landsman@nasa.gov>

W.Landsman (GSFC) and K. L. Page (U Leicester), on behalf of the 
Swift/UVOT team.

The Swift Ultra-Violet/Optical Telescope (UVOT) began settled 
observations of GRB 081016B (trigger 331856) 93 seconds after the BAT 
trigger (Page et al.,GCN Circ. 8381). No afterglow is detected at the 
enhanced XRT position (Osborne et al., GCN Circ. 8383) in the initial 
white finding chart or subsequent images. The limiting magnitudes 
(3-sigma in 3" radius 
apertures) in each of the UVOT filters are as follows:

Filter  T_start(s)  T_stop(s)  Exp(s)  Mag UL (3sig)

white       93       243       150     >21.5
b         4710      4823       113     >20.6
v         5373      5572       197     >20.0
u         5988     11724       960     >21.5
uvw1      5783      5982       197     >20.3
uvm2      5577      5777       197     >20.0
uvw2      5168      5368       197     >20.3

The values quoted above are in the UVOT photometric system (Poole et al. 
2008, MNRAS, 383, 627).  They are not corrected for the expected 
Galactic extinction corresponding to a reddening of E(B-V)=0.01 mag in 
the direction of the burst (Schlegel et al. 1998).