GCN Circular 7398

E. A. Hoversten (PSU) and J. R. Cummings (NASA/UMBC) report on behalf  
of the Swift UVOT team:

    The Swift/UVOT observed the field of GRB 080310 (trigger 305288)  
starting 99 seconds after the BAT trigger (Cummings, et al., GCN  
Circ. 7382
Not found
 
 
) starting with a 100s finding chart exposure in the white  
filter.  A bright afterglow was clearly detected in the initial white  
and V band exposures.

Further analysis shows that a fading source is detected at the XRT  
position in the U, B, V, and white filter images.  The source is  
still detectable in these filters around 7000 seconds after the  
burst.  The white and U band images show a brightening of the source  
reaching a peak after 1 ks after the burst before fading smoothly.   
The B and V images show a more smooth decay.

The afterglow is not detected in the UVW1 and UVM2 filters and is  
weakly detected in the UVW1 filter.  This is consistent with the  
measured redshift of 2.42 (Prochaska, et al., GCN Circ. 7388
Not found
 
 
).

The detections and 3-sigma upper limits in the UVOT photometric  
system (Poole, et al. 2008, MNRAS 383, 627) are given in the  
following table.  The white and optical magnitudes are individual  
exposures while the UV magnitudes are from co-added images.

Filter T_start(s) T_stop(s) Exposure(s)  Mag

white     99        197       98         18.50 +/- 0.06
white    868        967       98         17.95 +/- 0.05
white   6788       6985      197         18.99 +/- 0.07

v        208        602      393         17.38 +/- 0.05
v       7199       7334      135         18.5  +/- 0.3

b        685        695       10         17.7  +/- 0.2
b       6584       6780      197         18.9  +/- 0.1

u        660        680       19         17.8  +/- 0.2
u       1430       1450       19         17.3  +/- 0.2
u       6379       6575      197         18.3  +/- 0.1

uvw1     638       6373      452         20.3 +/- 0.3
uvm2     613       6168      197        >19.8
uvw2     716       7194      432        >20.8


No correction has been made for the expected Galactic extinction of E 
(B-V) of 0.04 mag in the direction of the burst (Schlegel, et al. 1998).