TITLE:   GCN CIRCULAR
NUMBER:  17828
SUBJECT: Swift/UVOT observations of GRB150518A
DATE:    15/05/19 14:27:38 GMT
FROM:    Massimiliano de Pasquale at IASF-Palermo  <mdp@ifc.inaf.it>

M. De Pasquale (MSSL-UCL) and B.Cenko (NASA-GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150518A
10383 s after the MAXI-GSC trigger (Kawamuro et al, GCN Circ. 17825).

No UVOT source is detected at the XRT position or within the XRT error
circle (Sbarufatti et al., GCN Circ. 17827) in the initial UVOT exposures.

Preliminary 3-sigma upper limit using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) is

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag U.L.

u                10383       20164          364            >20.3


The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).
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