GRB 110604A

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

K. Hurley and J. Goldsten, on behalf of the MESSENGER NS GRB team

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

A. von Kienlin, X. Zhang, and A. Rau, on behalf of the
INTEGRAL SPI-ACS GRB team

K. Yamaoka, M. Ohno, Y. Hanabata, Y. Fukazawa, T. Takahashi, M. Tashiro,
Y. Terada, T. Murakami, and K. Makishima, on behalf of the Suzaku WAM
team

At 14:49:45.666 GRB 110604A triggered Konus-Wind.  The Interplanetary
Network was alerted.  The burst was also detected by Swift-BAT,
MESSENGER (GRNS), Suzaku WAM, and INTEGRAL SPI-ACS.  Triangulation
yielded overlapping annuli that partly intersected the BAT field of
view.  A sub-threshold peak on the edge of the corresponding BAT image
was consistent with the annuli.  The BAT location is
RA, Dec 271.003, +18.472 or

RA (J2000)     18h 04m 00.7s
Dec (J2000)    18d 28' 19.2"

with an estimated uncertainty of 5 arcmin radius.

The burst was about 30 seconds long with 4 separated peaks.  The usual
detailed BAT products will not be available for this burst, since the
coding was only about 0.2%.

A Swift TOO request has been approved.

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 GRB 110604A (detected and localized by IPN
and Swift-BAT: Barthelmy et al., GCN 12063
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triggered Konus-Wind at T0=53385.666s UT (14:49:45.666)

The burst light curve consists of several multi-peaked pulses,
a total duration of the burst is ~45 s.
The emission is seen up to ~8 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB110604_T53385/

As observed by Konus-Wind the burst
had a fluence of (3.1 � 0.3)x10-5 erg/cm2,
and a 64-ms peak flux, measured from T0+2.880 s,
of (4.6 � 0.5)x10-6 erg/cm2/s
(both in the 20 keV - 5 MeV energy range).

The time-integrated spectrum of the burst
(from T0 to T0+37.376 s) is best fitted
in the 20 keV - 5 MeV range by the GRB (Band)
model, for which:
the low-energy photon index alpha = -1.10 (-0.08, +0.10),
the high energy photon index beta = -3.2 (<-2.6),
the peak energy Ep = 166(-16, +15) keV,
chi2 = 71.7/76 dof.

The spectrum at the maximum count rate
(measured from T0 to T0+5.376 s) is best fitted
in the 20 keV - 5 MeV range by the GRB (Band)
model, for which:
the low-energy photon index alpha = -0.8 (-0.1, +0.1),
the high energy photon index beta = -3.0 (-2.5, +0.3),
the peak energy Ep = 183(-14, +17) keV,
chi2 = 64.7/70 dof.

Also, both spectra show, in the 2-8 MeV range,
a hint of a weak additional hard spectral component.

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

B. Sbarufatti (INAF-OAB/IASFPA), J. Cummings (GSFC), M. De Pasquale 
(MSSL) report on behalf of the Swift Team.

We have analyzed 14.5 ks of Photon Counting data for GRB 110604A 
(Barthelmy et al., GCN 12063
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 ), observed from 138 ks to 425 ks after the 
Konus-Wind trigger.

We find a single, fading source inside the XRT field of view. Using 2497 
s of XRT Photon Counting mode data and 2 UVOT images, we find an 
astrometrically corrected X-ray position (using the XRT-UVOT alignment 
and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 
270.85885, +18.39961 which is equivalent to:

RA (J2000):   18h 03m 26s.12
Dec(J2000):  +18d 23' 58".6

with an uncertainty of 2.4 arcsec (radius, 90% confidence). This is 9.3 
arcmin away from the initial IPN position. The source was first detected 
at a level of (1.2+/-0.2)E-3 counts/s (equivalent to 5.1E-13 erg cm^-2 
s^-1), 138 ks after the trigger, and has faded to a level of 
(1.4+/-0.6)E-3 counts/s at 421 ks (equivalent to 6.0E-14 erg cm^-2 
s^-1). Another Swift observation is planned for June 14, 2011 in order 
to confirm fading.

No optical source is found within the XRT error circle. Preliminary 
3-sigma upper limits using the UVOT photometric system (Poole et al. 
2008, MNRAS, 383, 627) are:


Filter  T_start (s)   T_end (s)  Exp (s)  mag
white    207930       237252     1399     >22.9
v        208162       237295     516      >19.6
u        207698       240533     2864     >21.5


The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.24 in the direction of the 
burst (Schlegel et al. 1998).

This circular is an official product of the Swift-XRT team.

M. Akiyama, N. Ohmori, M. Yamauchi (Univ. of Miyazaki),
M. Ohno, T. Uehara, Y. Hanabata, T. Takahashi, Y. Fukazawa (Hiroshima U.),
S. Sugita (Nagoya U.), K. Yamaoka (Aoyama Gakuin U.), N. Vasquez (Tokyo Tech.),
Y. Terada, M. Tashiro, W. Iwakiri, K. Takahara, T. Yasuda (Saitama U.),
M. Kokubun, T. Takahashi (ISAS/JAXA), Y. E. Nakagawa (Waseda U.),
Y. Urata, P. Tsai, C-J. Chuang (NCU), K. Nakazawa, K. Makishima (Univ.
of Tokyo), on behalf of the Suzaku WAM team, report:

The bright GRB 110604A (IPN and Swift/BAT ; Barthelmy et al., GCN 12063
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triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy
range of 50 keV - 5 MeV at 14:49:42 UT (=T0).

The observed light curve shows a multi-peaked structure starting at
T0-13s, ending at T0+31s with a duration (T90) of about 27 seconds. There 
is a possible precursor at T0-13s with a duration of about 1 second. The
fluence in 100 - 1000 keV was 1.96 (-0.12, +0.10) x10^-5 erg/cm^2.
The 1-s peak flux measured from T0+2s was 7.68 (-0.98, +0.75) photons/cm^2/s
in the same energy range.

Preliminary result shows that the time-averaged spectrum including the precursor
from T0-13s to T0+31s is well fitted by a single power-law with a photon index
of 2.49 (-0.15, +0.17) (chi^2/d.o.f = 14.0/15).
All the quoted errors are at statistical 90% confidence level.

The light curves for this burst are available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html

B. Sbarufatti (INAF-OAB/IASFPA), J. Cummings (GSFC/UMBC), report on 
behalf of the Swift Team.

Swift-XRT performed further observations on the afterglow candidate 
announced in Sbarufatti et al. (GCN 12067
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 ). The source has faded with 
respect to the initial observation (1.2E-2 counts/s), and has dropped 
below the threshold for detection. The latest observations contain a 20 
ks exposure, corresponding to a 3-sigma upper limit of 1.3E-3 counts/s, 
confirming that the source was X-ray the afterglow of GRB 110604A.

This circular is an official product of the Swift-XRT team.