GCN Circular 8603

M. De Pasquale (MSSL/UCL) and A. Parsons (GSFC) reports, on the
behalf of the Swift UVOT team:

  Swift UVOT began settled exposures of GRB081203A (trigger 336489,
Parsons et al, GCN circular 8595
Not found
 
 
) 93 s after the burst trigger. A
bright optical transient is detected at the following coordinates:

RA = 15h 32m 07.58s (=233.031580), Dec = +63d 31m 14.9s (=63.520810) 
J2000

  with an uncertainty of 0.5'' (90% confidence level). This position is 
consistent with the XRT refined error circle (Goad et al, GCN circ 8598
Not found
 
 
).

  The source is detected in all filters but um2. Below, we show time of 
observations, the exposure time and the magnitude and 3 sigma upper
limits for this optical afterglow.



       T_start (s)   T_stop (s)   Exp (s)        Mag

  wh       93          242        146.2      14.53 +/- 0.01

  wh      586          605        19.5       13.91 +/- 0.01


  v       636          655        19.5       13.30 +/- 0.03


  b       561          580        19.5       13.53 +/- 0.01


  u       306          555         246       13.07 +/- 0.01

  u       709          728         19.5      13.53 +/- 0.02


  uw1     685          704         19.5      14.82 +/- 0.07


  um2     660          679         19.5          > 17.57

  um2     660         6008        412.6          > 20.1


  uw2     611          630         19.5       17.19 +/- 0.25



  The nondetection in the um2 filter is consistent with the
redshift z=2.1 derived from grism spectra (Landsman et al, GCN
circ 8601
Not found
 
 
). The detection in the uw2 filter is consistent with
this redshift due to the long-wavelength tail of the uw2
filter response.

  The above magnitudes have not been corrected for the Galactic
extinction corresponding to E(B-V) = 0.02 (Schlegel et al 1998)
The photometry is on the UVOT flight system described in Poole
et al (2008, MNRAS, 383,627)

[GCN OPS NOTE(03dec08):  Per author's request, the "A" was added to the burst name.]