GRB 110618A

K. Hurley, on behalf of the Mars Odyssey and MESSENGER GRB teams,

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

J. Goldsten, on behalf of the MESSENGER NS GRB 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, and A. Rau, on behalf of the
INTEGRAL SPI-ACS GRB team, 

V. Connaughton, M. Briggs, and C. Meegan, on behalf of the Fermi
GBM team, and

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

On 2011 June 18 at 08:47:25 UT, an extremely intense, long duration GRB
was observed by Fermi (GBM), INTEGRAL (SPI-ACS), Konus-Wind, MESSENGER,
Mars Odyssey, and Swift (outside the coded field of view).  We have
triangulated it to the following 3 sigma error box, whose area is 1.41
square degrees:

-----------------------------------------------
    RA(2000), deg              Dec(2000), deg
-----------------------------------------------
Center:
  176.808 (11h 47m 14s)   -71.688 (-71d 41' 16")
Corners:
  176.474 (11h 45m 54s)   -70.272 (-70d 16' 19")
  175.222 (11h 40m 53s)   -71.703 (-71d 42' 12")
  177.247 (11h 48m 59s)   -73.095 (-73d 05' 42")
  178.392 (11h 53m 34s)   -71.659 (-71d 39' 33")
-----------------------------------------------

Some improvement in this localization is possible.  The spectral and
temporal properties of this burst will appear in a forthcoming GCN.

S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin,
P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf
of the Konus-Wind team, report:

The long hard GRB 110618A (localized by IPN: Hurley et al., GCN 12077
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 )
triggered Konus-Wind at T0=31673.867 s UT (08:47:53.867)

The burst light curve consists of a single long hard pulse
with unusually gentle onset and a total duration of ~250 s.
The emission is seen up to ~5 MeV, a hard-to-soft spectral
evolution is noticeable in the course of the event.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB110618_T31673/

As observed by Konus-Wind the burst
had a fluence of (1.1 � 0.1)x10-4 erg/cm2,
and a 256-ms peak flux, measured from T0+1.280 s,
of (2.0 � 0.2)x10-6 erg/cm2/s
(both in the 20 keV - 5 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+229.632 s) is best fitted
in the 20 keV - 5 MeV range by a power law
with exponential cutoff model, for which
alpha = -1.40 (-0.08, +0.10),
and Ep = 569(-160, +304) keV,
chi2 = 78.1/73 dof.

The spectrum at the maximum count rate
(measured from T0 to T0+8.448 s) can be fitted
in the 20 keV - 5 MeV range by a power law
with exponential cutoff model, for which
alpha = -1.12 (-0.06, +0.06),
and Ep = 524(-96, +138) keV,
chi2 = 88.7/73 dof.

All the quoted results are preliminary.
All the quoted errors are at the 90% confidence level.

B. E. Cobb (GWU), reports:

Using the ANDICAM instrument on the SMARTS 1.3m telescope at CTIO,
we obtained optical imaging of part of the error region of GRB 110618A
(GCN 12077
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 , Hurley et al.) approximately 113 hours (4.7 days)
post-burst. Nine individual 5-minute I-band exposures were
obtained, tiled around the center of the IPN error region
(RA/Dec: 11h47m14s -71d41'16").  Each image is 6'x6', so these
images cover approximately 0.09 square degrees, e.g. the central 6% of
the IPN error region.

Preliminary visual comparison to the DSS reveals no new optical
sources in the SMARTS images (limited by the slightly shallower depth
of the DSS imaging).  This does not rule out the possibility of
an afterglow candidate contained in a relatively bright host
galaxy (additional SMARTS imaging is being obtained for further
analysis).