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GCN Circular 21572

Subject
LIGO/Virgo G298048: Continued Swift UV and X-ray Monitoring of SSS17a
Date
2017-08-18T18:32:37Z (7 years ago)
From
Brad Cenko at NASA/GSFC <brad.cenko@nasa.gov>
S. B. Cenko (NASA/GSFC), S.W.K. Emery (UCL-MSSL), S. Campana (INAF-OAB),��P.A. Evans (U. Leicester), J.A. Kennea (PSU), A.A. Breeveld (UCL-MSSL), E. Troja��(NASA/GSFC/UMCP), P.T. O'Brien (U. Leicester), S.D. Barthelmy��(NASA/GSFC), A.P. Beardmore (U. Leicester), D.N. Burrows (PSU), G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB),��V.D'Elia(ASDC), P. Giommi (ASI), C. Gronwall��(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), J.A.��Nousek (PSU), S.R. Oates (U. Warwick), 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), A. Tohuvavohu (PSU) report��on behalf of the Swift team:��

We obtained a second epoch of UV and X-ray imaging of SSS17a (Coulter et al.; GCN 21529), the candidate optical counterpart of G298048 (LVC; GCN 21509) with the Swift Gamma-Ray Burst Explorer.  Observations began��at 13:30 UT��on 2017��August 18.  Compared with our previous epoch of imaging (Evans et al.; GCN 21550), the source has faded significantly at UV wavelengths.  Specifically we measure the following magnitudes (with no host subtraction):

Filter T_start(s) T_stop(s) Exp(s) Mag (Vega)��

u��   90029 90164  133��17.42 +/- 0.09��
uvw1��89755 90024  265��18.50 +/- 0.15��
uvm2��89346 94665 1045��20.40 +/- 0.27��
uvw2��90170 90674  496��20.37 +/- 0.32��

Given the relatively flat evolution in the optical and NIR, this suggests significant cooling in the source.

The source remains undetected in the X-rays, with comparable limits to our previous epoch.

Further observations are planned.
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