[vsnet-grb-info 7022] Swift/UVOT detection of GRB081203B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8606
SUBJECT: Swift/UVOT detection of GRB081203B
DATE:    08/12/04 00:37:27 GMT
FROM:    Patricia Schady at MSSL/Swift  <ps at mssl.ucl.ac.uk>

P. Schady (MSSL-UCL), F.E. Marshall (NASA/GSFC) and B. Sbarufatti  
(INAF-IASF Pa) report on behalf of the Swift/UVOT team:

The Swift/UVOT began white band observations of the field of the Swift  
BAT Slew Survey (BATSS) GRB 081203B 4.6 hrs after the BAT trigger  
(Copete et al., GCN Circ. 8600, 8602). An uncatalogued, fading source  
is clearly detected at

RA(J2000.0)  =   15:15:11.67 (228.79863 deg)
DEC(J2000.0) = +44:25:42.9 (44.42859 deg)

with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence),  
consistent with the UVOT-enhanced XRT position (Sbarufatti et al., GCN  
Circ. 8605).

The magnitudes of the first and last UVOT white band observations are  
reported below:

Filter    T_mid (s)   Exp (s)     Magnitude
white       16746       154        18.29 +/- 0.04
white       22270       441        18.70 +/- 0.03

indicating a decay rate of alpha~1.0. The above magnitudes are not  
corrected for the Galactic extinction corresponding to a reddening of  
E_{B-V} = 0.02 mag (Schlegel et al., 1998, ApJS, 500, 525).  The  
photometry is on the UVOT flight system described in Poole et al.  
(2008, MNRAS, 383,627).