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GCN Circular 20400

LIGO/Virgo G268556: Swift/UVOT observations of ATLAS17aeu
2017-01-08T18:31:44Z (7 years ago)
Samantha Oates at U of Warwick <>
S.R. Oates (Uni. of Warwick), A. A. Breeveld (MSSL-UCL), 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. Evans (U Leicester),
N. Gehrels (NASA/GSFC), P. Giommi (ASI), C. Gronwall (PSU), J. Kennea (PSU),
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 targetted observations of the field of ATLAS
transient ATLAS17aeu (Tonry et al., LVC Circ. 20382) from 00:00 UT to
01:35 UT on 2017 Jan 7 and again between 16:01 UT on 2017 Jan 7 to
01:30 on 2017 Jan 08. No optical afterglow consistent with the ATLAS
position or 'source5' of the XRT follow up of G268556 (Evans et al.,
GCN Circ. 20390) is detected in the UVOT exposures at more than 3 sigma.
We do note however a source at 2.9 sigma in the w2 filter, which in comparison
to the second observation appears to have faded.

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

Filter    T_start(UT)  T_stop(UT)  Exp(s)    Mag/3sigUL
v          7.007           7.009          144       > 19.1
v          7.667           7.936          1009      > 20.3

u          7.018           7.019          106      > 18.6
u          7.881           8.016          311       > 19.2

w1         7.014           7.018          290       > 19.5
w1         7.876           7.947          801       > 20.2

m2         7.009           7.014          435       > 20.0
m2         7.670           7.943          2413      > 21.2

w2         7.000           7.067          690       > 20.7   (20.76 +/- 0.37 detection at 2.9 sigma)
w2         7.658          8.069          5177      > 22.0   (22.41 +/- 0.53 detection at 2.1 sigma)

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.03 in the direction of the transient
(Schlegel et al. 1998).

[GCN OPS NOTE(08jan17): Per author's request, PE and JK were added
to the author list.]
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