LIGO/Virgo S190425z: Swift/BAT Counterpart Search

<somebody goes first>
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 S190425z (LIGO/VIRGO Collaboration GCN Circ. XXXXX), 
where T0 is the LVC trigger time (2019-04-25T08:18:05 UTC).

The center of the BAT FOV at T0 is
RA = 123.263 deg,
DEC = 22.657 deg,
ROLL = 279.608 deg.
The BAT Field of View (>10% partial coding) covers 11.80% of the integrated
LVC localization probability, and 0.18% of the galaxy convolved 
probability (Evans et al. 2016).

[If there are significant detection, change the following paragraph accordingly]
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 ~  x 10^0 erg/s/cm^2.

[Description of event data analysis, if available]

BAT retains decreased, but significant, sensitivity to rate increases for
gamma-ray events outside of its FOV. About 62.15% 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.