TITLE:   GCN CIRCULAR
NUMBER:  22847
SUBJECT: AT2018cow: Swift/BAT data search
DATE:    18/06/26 02:13:12 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), A. Tohuvavohu (PSU),
S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF/USRA), R. Margutti (Northwestern University),
C. B. Markwardt (GSFC), T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

We report the search results of AT2018cow in the Swift/BAT data.
Using the source location of (RA, Dec) = (244.00090, 22.26800) deg
from Smartt et al. ATel #11727, the BAT mask-weighted light curve
from the BAT survey data (14-195 keV) shows marginal detections
of AT2018cow at ~ 3 sigma at ~T0, ~T0+1, and ~T0+6 days.
T0 = 2018-06-16 at 10:35:02 UTC, which is the time of discovery
reported in Smartt et al. ATel #11727.

The 3 sigma detections are roughly consistent with NuSTAR flux
measurements (Margutti et al., ATel #11775). However, we note that
due to the low significance of these detections, we cannot rule out that
these are due to noise fluctuation.

A search with the BAT onboard sub-threshold triggers found no events
with localizations that are consistent with AT2018cow.

The results of the BAT data analysis are at
https://swift.gsfc.nasa.gov/results/BATbursts/AT2018cow/top.html

The light curves and data will continue to be updated on a daily
basis in the near future.