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GCN Circular 21235

LIGO/Virgo G288732: Swift/UVOT follow up of the possible LAT counterpart
2017-06-09T16:13:55Z (7 years ago)
Samantha Oates at U of Warwick <>
S.W.K. Emery (UCL-MSSL), S.R. Oates (Uni. of Warwick), 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), P.A. Evans (U. Leicester), P. Giommi (ASI), C. Gronwall (PSU),
J.A. Kennea (PSU), H.A. Krimm (CRESST/GSFC/USRA), N.P.M. Kuin (UCL-MSSL),
A.Y. Lien (GSFC/UMBC), 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 a four-pointing follow up of the possible LAT source in
the error region of GW trigger G288732 (Omodei et al., LVC Circ. 21227). The
observations currently span from 62.8 ks to 86.3 ks after the LVC trigger. We detect
optical sources in the XRT error circles of 'source 3', 'source 6' and 'source 7', but
these are also present in the SDSS catalogue and we do not find evidence of fading.
Additionally, the XRT error circle for 'source 5' is on the edge of the UVOT detector,
but we do not see any optical source in the error circle. We do not find any optical
afterglow consistent with the LAT position or 'source 1', 'source 2' and 'source 4' of
the XRT follow up of G288732 (Evans et al., GCN Circ. 21233) in the UVOT exposures
at more than 3 sigma.

Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the
exposures are:

XRT_source      Filter    T_start(s)  T_stop(s)  Exp(s)    Mag/3sigUL

1       u          63081           85743          1737      > 20.8
2       u          62802           85173          1764      > 20.5
4       u          62942           86261          1710      > 20.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the transient
(Schlegel et al. 1998).
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