GCN Circular 20536

A. A. Breeveld (MSSL-UCL), S.R. Oates (U. Warwick), N.P.M. Kuin 
(UCL-MSSL), S.D. Barthelmy (NASA/GSFC), A.P. Beardmore (U. Leicester), 
D.N. Burrows (PSU), S. Campana (INAF-OAB), S.B. Cenko (NASA/GSFC), G. 
Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), 
V.D'Elia (ASDC), P.A. Evans (U. Leicester), N. Gehrels (NASA/GSFC), P. 
Giommi (ASI), C. Gronwall (PSU), J.A. Kennea (PSU), H.A. Krimm 
(CRESST/GSFC/USRA), A.Y. Lien (GSFC/UMBC), D. Malesani (DARK/NBI), F.E. 
Marshall (NASA/GSFC), A. Melandri (INAF-OAB), B. Mingo (U. Leicester), 
J.A. Nousek (PSU), P.T. O'Brien (U. Leicester), J.P. Osborne (U. 
Leicester), C. Pagani (U. Leicester), K.L. Page (U.Leicester), D.M. 
Palmer (LANL), M. Perri (ASDC), J.L. Racusin (NASA/GSFC), B. Sbarufatti 
(INAF-OAB/PSU), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja 
(NASA/GSFC/UMCP) report on behalf of the Swift team:

The Swift/UVOT performed targeted observations of the transient PS17yt 
(Chambers et al., LVC Circ. 20512), within the error area of the LIGO 
event G270580, between 17:25:31 and 19:27:09 on 24th January 2017 in the 
UVW2 filter. The preliminary combined magnitude using the UVOT 
photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for 
the exposures is 20.9 �� 0.2 mag.