TITLE:   GCN CIRCULAR
NUMBER:  20473
SUBJECT: LIGO/Virgo G268556: Swift-XRT observations of iPTF17cw
DATE:    17/01/16 19:47:25 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A Evans (U. Leicester), A. Corsi (TTU), J.A. Kennea (PSU), S.D. 
Barthelmy (NASA/GSFC), A.P. Beardmore (U. Leicester), A.A. Breeveld 
(UCL-MSSL), 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), N. Gehrels (NASA/GSFC), P. Giommi 
(ASI), C. Gronwall (PSU), H.A. Krimm (CRESST/GSFC/USRA), N.P.M. Kuin 
(UCL-MSSL), 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), S.R. Oates (U. Warwick), P.T. O'Brien (U.  Leicester), 
J.P. Osborne (U. Leicester), C. Pagani (U. Leicester), K.L.
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), M.M. Kasliwal (Caltech), S.R. Kulkarni (Caltech), D.A. 
Frail (NRAO), N.T. Palliyaguru (TTU) report on behalf of the Swift and 
iPTF GW follow-up teams:

Swift has performed follow-up observations of the source iPTF17cw 
(Kasliwal et al., LVC Circ. 20398; Kupfer et al., LVC Circ. 20419). 
Swift-XRT collected 1.3 ks of data from 790.6 ks to 802.8 ks after the 
GW trigger.

No X-ray events were detected at the location of iPTF17cw. The 3-sigma 
upper limit at this location was 5.3e-3 ct/sec (0.3-10 keV). Assuming a 
typical AGN spectrum (NH=3e20 cm^-2, Gamma=1.7) this corresponds to a 
flux of 2.19e-13 erg cm^-2 s^-1.