TITLE: GCN CIRCULAR NUMBER: 24863 SUBJECT: LIGO/Virgo S190426c: Swift UVOT - no new counterpart candidates identified DATE: 19/06/20 13:55:26 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL), A. A. Breeveld (MSSL-UCL), C. Gronwall (PSU), F. E. Marshall (NASA/GSFC), S. R. Oates (Uni. of Warwick), M.J. Page (UCL-MSSL), M. de Pasquale (Istambul U), M. H. Siegel (PSU), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), 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), V. D'Elia(ASDC), P. A. Evans (U. Leicester), P. Giommi (ASI), D. Hartmann (Clemson U.), J. A. Kennea (PSU), H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC), D. B. Malesani (DTU Space), A. Melandri (INAF-OAB), 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), T. Sakamoto (AGU), B. Sbarufatti (INAF-OAB/PSU), G. Tagliaferri (INAF-OAB), A. Tohuvavohu (PSU), and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team: The Swift UVOT instrument started follow up observations of the LIGO-Virgo event S190426c (LVC GCN Circ. No. 24237) at 2019-04-26 17:45:00 UT 142 minutes after the event. Observations continued for about 48 hours (Tohuvavohu et al., GCN Circ. No. 24353). The UVOT approach for searching for the ultraviolet-optical counterpart has been described in Kuin et al. (GCN Circ. No. 24767). The limiting magnitude can vary but typically is 18.6th magnitude (Vega). In the 894 fields that were observed, UVOT detected 1008 galaxies and 130 counterpart candidates but none of the counterpart candidates from the automated processing proved to be a viable source. Neither did the additional inspection of the imaged galaxies lead to a candidate missed by the automated processing.