TITLE:   GCN CIRCULAR
NUMBER:  17349
SUBJECT: GRB 150123A: Swift/UVOT observations
DATE:    15/01/24 12:49:07 GMT
FROM:    Samantha Oates at MSSL  <sro@mssl.ucl.ac.uk>

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

The Swift/UVOT began settled observations of the field of MAXI GRB 150123A
8.7ks after the trigger. No optical afterglow is detected within the MAXI 
error circle (Fukushima, GCN Circ. No. 17345). Using the UVOT photometric 
system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) We obtain a typical 
3 sigma upper limit of >20.6 in the u filter. This magnitude has not been corrected 
for the Galactic extinction due to the reddening of E(B-V) = 0.04 in the direction 
of the burst (Schlegel et al. 1998).

In the error circles for XRT candidates #1, #2, and #3 we note the presence of objects 
that are catalogued in the USNO-B1, as discussed in Melandri et al. (GCN Circ. No. 17348). 
At the present time we cannot determine if any of these objects are fading.