TITLE:   GCN CIRCULAR
NUMBER:  15888
SUBJECT: IPN triangulation of GRB 140226A, a possible GRB counterpart to iPTF14yb
DATE:    14/02/28 00:25:44 GMT
FROM:    Kevin Hurley at UCBerkeley/SSL  <khurley@ssl.berkeley.edu>

K. Hurley, on behalf of the Interplanetary Network,

S. Golenetskii, R. Aptekar, V. Pal'shin, D. Frederiks, 
D. Svinkin, and T. Cline on behalf of the Konus-Wind team,

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,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C.
Ferrigno, on behalf of the INTEGRAL SPI-ACS 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, and V. Pelassa, on behalf of the Fermi
GBM team, report:

We have examined IPN data for the period 2014-02-26T09:05:00 to
2014-02-26T10:18:00, when the optical transient source iPTF14yb was
discovered (Cenko et al. GCN 15883).  During this time, Konus, Swift,
INTEGRAL, RHESSI, Odyssey, and MESSENGER were operating and returning
data, although in the presence of increased solar activity.  Suzaku was
off.  We have identified one event, at 2014-02-26T10:02:57 (36177 s),
observed by Odyssey, INTEGRAL (SPI-ACS) and Konus (in the waiting
mode), whose duration is ~15 s, and whose localization is consistent
with iPTF14yb.  Specifically, the Odyssey-INTEGRAL triangulation
annulus is centered at RA, Dec = 206.305 degrees (13 h 45 m 13.2 s),
-7.925 degrees (-7 o 55 ' 29 "), with radius 27.577 +/- 0.607 degrees
(3 sigma).  iPTF14yb lies 0.157 degrees from the center line of the
annulus.  The probability that the transient lies within the annulus by
chance is roughly 0.005.  At the time of this event, the optical
transient was below the horizon for Swift, and no emission consistent
with a GRB was seen in the data. Fermi was in the SAA.  The RHESSI and
MESSENGER backgrounds were high and variable due to solar activity,
making the identification of this burst uncertain in their data.

If this is indeed the GRB counterpart to iPTF14yb, this would appear to
be the first GRB to be discovered on the basis of its optical
counterpart.

This triangulation can be improved.  Detailed spectral and temporal
information on this burst will be presented in a forthcoming GCN
Circular.