TITLE:   GCN CIRCULAR
NUMBER:  9527
SUBJECT: GRB090618: Swift/UVOT bright afterglow detection
DATE:    09/06/18 19:00:10 GMT
FROM:    Patricia Schady at MSSL/Swift  <ps@mssl.ucl.ac.uk>

P. Schady (MSSL-UCL) reports on behalf of��the Swift UVOT team:

The Swift/UVOT began settled observations of the field of GRB 090618 129s 
after the BAT trigger (Schady et al., GCN Circ. 9512) and a 
decaying��source is detected in all UVOT filters at the position reported 
in Schady et al. (GCN Circ. 9512), consistent with refined XRT error 
circle��(Evans et al., GCN Circ. 9521) as well as the optical afterglow 
position reported in a number of other GCNs (GCN Circ. 9512, 9514, 9515). 
The detection of the afterglow of GRB 090618 in all filters puts��an upper 
limit on the redshift��of z < 1.7, consistent with the redshift constraints 
reported by Cenko et al. (GCN Circ. 9518).

The magnitudes for the first UVOT observation of GRB 090618 in each filter 
are as follows:

Filter  T_start(s)  T_stop(s)  Exp(s)      Mag
white      129        279       147    14.27+/-0.01
v          671        691       19     15.60+/-0.09
b          596        616       19     15.92+/-0.06
u          340        590       246    14.62+/-0.01
uvw1       720        740       19     15.09+/-0.08
uvm2       695        715       19     15.23+/-0.12
uvw2       647        667       19     15.27+/-0.10

The values quoted above are not corrected for the Galactic extinction due 
to the reddening of E(B-V) = 0.09 in the direction of the burst 
(Schlegel��et al. 1998). The photometry is on the UVOT photometric system 
described��in Poole et al. (2008, MNRAS, 383, 627).