TITLE:   GCN CIRCULAR
NUMBER:  19426
SUBJECT: Interplanetary Network Search for IceCube 160427A
DATE:    16/05/12 18:05:09 GMT
FROM:    Kevin Hurley at UCBerkeley/SSL  <khurley@ssl.berkeley.edu>

D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, and T. Cline,
on behalf of the Konus-Wind team,

K. Hurley, on behalf of the Interplanetary Network,

I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on
behalf of the GRS-Odyssey GRB team,

S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of
the Swift-BAT team, and

V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa, and A. Goldstein, 
on behalf of the Fermi GBM team, report:

We have searched for an electromagnetic counterpart to the IceCube
neutrino event 160427A (GCN 19363) in the data of the six-spacecraft
Interplanetary Network.  INTEGRAL SPI-ACS and RHESSI were not taking
data at the time of the event. Konus-Wind, Swift BAT, Odyssey HEND, and
Fermi GBM (GCN 19364) were taking data and the source direction was
unocculted to them.  No events were found which could reasonably be
associated with 160427A.  Specifically, the following limits can be
derived from the Konus Wind data.  These apply to a 1000 s interval
centered at 05:52:32 UT (an interval duration consistent with the
expected delay of neutrino signals from GRBs, Baret et al., 2011,
arXiv:1101.4669), using standard KW GRB search procedures at a 5 sigma
threshold.

The 90% fluence upper limits for a typical short GRB spectrum (CPL with
alpha=-0.5, Ep=500 keV) over a 2.944 s time scale is ~1.0x10^-7
erg/cm2.  This limit was calculated using count rates in the bins from
T0-1.524 s to T0+1.420 s (corrected for Konus to Earth time of
flight).

For a typical long GRB spectrum (Band function with alpha=-1,
beta=-2.5, Ep=300 keV) and a search interval duration of 24 s (a
typical KW long GRB duration) the upper limit is ~1.5x10^-6 erg/cm2.
Both limits are in the 10 keV - 10 MeV band.

The two Konus-Wind triggers closest in time to 160427A were at 2016-04-27 37785.294 s UT
(10:29:45.294) in the S1 detector (4.5 hours after the IceCube event)
and 2016-04-25 69940.132 s UT (19:25:40.132) in the S2 detector (about
two days before the event).  The localization of GRB 20160427_37785 is
inconsistent with the neutrino event, while the ecliptic latitude
response for GRB 20160425_T69940 is consistent with it, but the
probability of a random coincidence is high. GRB 20160425_T69940 was
not detected by any other instrument, so no further analysis is possible.