{
  "bibcode": "2019GCN.25846....1S",
  "body": "T. Sakamoto (AGU), S. D. Barthelmy (NASA/GSFC),\nA. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL),\nA. P. Beardmore (U. Leicester), M. G. Bernardini (INAF-OAB),\nA. A. Breeveld (MSSL-UCL), D. N. Burrows (PSU),\nS. Campana (INAF-OAB), S. B. Cenko (NASA/GSFC),\nG. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA),\nP. D'Avanzo (INAF-OAB), V. D'Elia (ASI-SSDC), S. Emery (UCL-MSSL),\nP. A. Evans (U. Leicester), P. Giommi (ASI), C. Gronwall (PSU),\nD. Hartmann (Clemson U.), J. A. Kennea (PSU),\nN. Klingler (PSU), H. A. Krimm (NSF),\nN. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC),\nA. Melandri (INAF-OAB), J. A. Nousek (PSU),\nS. R. Oates (Uni. of Warwick), P. T. O'Brien (U. Leicester),\nJ. P. Osborne (U. Leicester), C. Pagani (U. Leicester),\nK. L. Page (U.Leicester), M. J. Page (UCL-MSSL), M. Perri (ASDC),\nJ. L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU),\nM. H. Siegel (PSU), G. Tagliaferri (INAF-OAB), A. Tohuvavohu (Toronto),\nE. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team:\n\nWe report the search results in the BAT data within T0 +/- 100 s of the\nLVC event S190923y (LIGO/VIRGO Collaboration GCN Circ. 25814),\nwhere T0 is the LVC trigger time (2019-09-23T12:55:59.645 UTC).\n\nThe center of the BAT field of view (FOV) at T0 is\nRA = 5.951 deg,\nDEC = -1.780 deg,\nand the roll angle is 107.879 deg.\nThe BAT FOV (>10% partial coding) covers 0.00% of the integrated\nLVC localization probability, and 0.00% of the galaxy convolved\nprobability (Evans et al. 2016). Note that the sensitivity in the BAT FOV\nchanges with the partial coding fraction. Please see the BAT FOV figure\nin the summary page (link below) for the specific location of the LVC\nregion relative to the BAT FOV.\n\nWithin T0 +/- 100 s, no significant detections (signal-to-noise ratio\n>~ 5 sigma) are found in the BAT raw light curves with time bins of 64 ms,\n1 s, and 1.6 s. Assuming an on-axis (100% coded) short GRB with a typical\nspectrum in the BAT energy range (i.e., a simple power-law model with a\npower-law index of -1.32, Lien & Sakamoto et al. 2016), the 5-sigma upper\nlimit in the 1-s binned light curve corresponds to a flux upper\nlimit (15-350 keV) of ~ 7.56 x 10^-8 erg/s/cm^2.\nAssuming a luminosity of ~ 2 x 10^47 erg/s (similar to GW170817)\nand an average Epeak of ~ 400 keV for short GRBs (Bhat et al. 2016),\nthis flux upper limit corresponds to a distance of ~ 82.64 Mpc.\n\nEvent data are available from T0-101.32 to T+98.757. No significant\ndetections are found in the 15-350 keV images created using intervals of\nT0 to T0+0.1 s, T0-2 s to T0+8 s, and the whole event data range.\n\nBAT retains decreased, but significant, sensitivity to rate increases for\ngamma-ray events outside of its FOV. About 99.92% of the integrated LVC\nlocalization probability was outside of the BAT FOV but above the\nEarth's limb from Swift's location, and the corresponding flux upper limits\nfor this region are within roughly an order of magnitude higher than those\nwithin the FOV.\n\nThe results of the BAT analysis are available at\nhttps://swift.gsfc.nasa.gov/results/BATbursts/team_web/S190923y/web/source_public.html",
  "circularId": 25846,
  "createdOn": 1569461627000,
  "email": "amy.y.lien@nasa.gov",
  "subject": "LIGO/Virgo S190923y: no counterpart candidates in the Swift/BAT observations",
  "submitter": "Amy Lien at GSFC  <amy.y.lien@nasa.gov>",
  "eventId": "LIGO/Virgo S190923y"
}