[vsnet-grb-info 22997] LIGO/Virgo S190718y: No counterpart candidates in the Swift/BAT Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25096
SUBJECT: LIGO/Virgo S190718y: No counterpart candidates in the Swift/BAT Observations
DATE:    19/07/19 00:27:17 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien at nasa.gov>

D. M. Palmer (LANL), S. D. Barthelmy (NASA/GSFC),
A. Y. Lien (GSFC/UMBC), T. Sakamoto (AGU),
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 (ASI-SSDC), 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), 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. J. Page (UCL-MSSL), 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 S190718y (LIGO/VIRGO Collaboration GCN Circ. 25087),
where T0 is the LVC trigger time (2019-07-18T14:35:12.067 UTC).

The center of the BAT FOV at T0 is
RA = 357.719 deg,
DEC = -45.287 deg,
and the ROLL angle is 94.804 deg.
The BAT Field of View (>10% partial coding) covers 6.27% of the integrated
LVC localization probability, and 11.94% of the galaxy convolved
probability (Evans et al. 2016).

Swift/BAT was in SAA during this time. Within T0 +/- 100 s, no significant
detections are found in the BAT raw light curves with time bins of 64 ms,
1 s, and 1.6 s. The flux upper limit estimation is unavailable due
to the rapid increase of background during the SAA.

BAT retains decreased, but significant, sensitivity to rate increases for
gamma-ray events outside of its FOV. About 23.33% 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/S190718y/web/source.html