[vsnet-grb-info 7489] GRB 090328: Swift UVOT observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9048
SUBJECT: GRB 090328: Swift UVOT observations
DATE:    09/03/29 15:11:20 GMT
FROM:    Samantha Oates at MSSL  <sro at mssl.ucl.ac.uk>

S. R. Oates (MSSL-UCL) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began observing the field of GRB 090328 16 hrs
after the Fermi LAT trigger (McEnery et al., GCN 9044). We detect
a candidate optical afterglow in the u and white filters at:

RA(J2000.0)  = 06:02:39.67
DEC(J2000.0) = -41:52:54.5

with an estimated uncertainty of 0.6 arcsec (radius, 90% confidence).
At the moment we are unable to tell if the source is fading, further
observations have been performed, but due to a data gap, the data
is currently unavaliable.

Preliminary magnitudes for the white and u filters are:

Filter    T_mid (hrs)  Exposure(s)       Mag  Err
------------------------------------------------------------
u         16.0         793           19.04 +/- 0.13
white     16.1         173           19.56 +/- 0.14

The above magnitudes are not corrected for the Galactic extinction
corresponding to a reddening of E_{B-V} = 0.06 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).