[vsnet-grb-info 22945] LIGO/Virgo S190707q: No counterpart candidates in the Swift/BAT Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25044
SUBJECT: LIGO/Virgo S190707q: No counterpart candidates in the Swift/BAT Observations
DATE:    19/07/09 23:43:01 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto at phys.aoyama.ac.jp>

A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (NASA/GSFC),
D. M. Palmer (LANL), 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 S190707q (LIGO/VIRGO Collaboration GCN Circ. 25012),
where T0 is the LVC trigger time (2019-07-07T09:33:26.181 UTC).

The center of the BAT FOV at T0 is
RA = 143.593 deg,
DEC = -17.350 deg,
ROLL = 321.495 deg.
The BAT Field of View (>10% partial coding) covers 36.58% of the integrated
LVC localization probability, and 39.33% 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 ~ 7.74 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 21.81% 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/S190707q/web/source.html