TITLE: GCN CIRCULAR NUMBER: 21483 SUBJECT: LIGO/Virgo G297595: Swift/BAT data search DATE: 17/08/14 20:48:48 GMT FROM: Amy Lien at GSFC/Swift 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), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), 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), 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 G297595 (LIGO/VIRGO Collaboration GCN Circ. 21474), where T0 is the LVC trigger time (2017-08-14T10:30:43 UTC). The BAT pointing position at T0 is RA = 195.263 deg, DEC = 27.016 deg, ROLL = 255.372 deg. The BAT Field of View (>10% partial coding) covers 0.0% of the integrated LVC localization probability. That is, there is no overlap between the BAT field of view and the LVC probability region at T0. 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 1 s and 1.6 s. There is a ~ 5.4 sigma spike at T0+27 s. However, since this spike is only seen in one single time bin and the 100-350 keV band, it is likely due to noise fluctuation. We do not have event data around this time for further analysis. 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 ~ 7.68 x 10^-8 erg/s/cm^2. BAT retains decreased, but significant, sensitivity to rate increases for gamma-ray events outside of its FOV. About 0.13% 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 of those within the FOV.