TITLE: GCN CIRCULAR NUMBER: 24518 SUBJECT: LIGO/Virgo S190512at: Swift/BAT Counterpart Search DATE: 19/05/13 15:22:16 GMT FROM: Amy Lien at GSFC T. Sakamoto (AGU), S. D. Barthelmy (NASA/GSFC), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), A. A. Breeveld (MSSL-UCL), 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), S. Emery (UCL-MSSL), P. A. Evans (U. Leicester), P. Giommi (ASI), C. Gronwall (PSU), D. Hartmann (Clemson U.), J. A. Kennea (PSU), H. A. Krimm (NSF), N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), B. Mingo (U. Leicester), J. A. Nousek (PSU), S. R. Oates (Uni. of Warwick), P. T. O'Brien (U. Leicester), J. P. Osborne (U. Leicester), C. Pagani (U. Leicester), K. L. Page (U.Leicester), M. Perri (ASDC), J. L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU), G. Tagliaferri (INAF-OAB), A. Tohuvavohu (PSU), E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team: We report the search results in the BAT data within T0 +/- 100 s of the LVC event S190512at (LIGO/VIRGO Collaboration GCN Circ. 24503), where T0 is the LVC trigger time (2019-05-12T18:07:14.422 UTC). The center of the BAT FOV at T0 is RA = 92.704 deg, DEC = -30.367 deg, ROLL = 302.899 deg. The BAT Field of View (>10% partial coding) covers 0.00% of the integrated LVC localization probability, and 0.00% of the galaxy convolved probability (Evans et al. 2016). Within T0 +/- 100 s, no significant detections (signal-to-noise ratio >~ 5 sigma) are found in the BAT raw light curves with time bins of 64 ms, 1 s, and 1.6 s. Assuming an on-axis (100% coded) short GRB with a typical spectrum in the BAT energy range (i.e., a simple power-law model with a power-law index of -1.32, Lien & Sakamoto et al. 2016), the 5-sigma upper limit in the 1-s binned light curve corresponds to a flux upper limit (15-350 keV) of ~ 7.12 x 10^-8 erg/s/cm^2. No event data are available at this point. BAT retains decreased, but significant, sensitivity to rate increases for gamma-ray events outside of its FOV. About 94.73% of the integrated LVC localization probability was outside of the BAT FOV but above the Earth's limb from Swift's location, and the corresponding flux upper limits for this region are within roughly an order of magnitude higher than those within the FOV. The results of the BAT analysis are available at https://swift.gsfc.nasa.gov/results/BATbursts/team_web/S190512at/web/source.html