V. Savchenko, C. Ferrigno, E. Bozzo, M. Nikolajuk, M. Beck (ISDC), S.
Mereghetti (INAF/IASF-Milano). V. Beckmann (APC), Arne Rau (MPE), J.
Borkowski (CAMK/Torun), D. G=F6tz (CEA/Saclay), and A. von Kienlin (MPE)
report on behalf of the INTEGRAL SPI-ACS GRB team:
An exceptionally bright burst has been detected by the SPI
Anti-Coincidence System (ACS) on-board INTEGRAL at 2011-04-06T03:44:10.
The SPI-ACS light curve shows a single smooth peak with a peak
count rate of ~19000 counts/50msec of a duration of about 3 seconds.
The roughly estimated energy peak flux is of the order of 6e-5
erg/cm2/s. This was one of the brightest bursts ever detected with SPI-AC=
S.
The SPI-ACS light curves are available (both as images and data files)
at http://isdc.unige.ch/Soft/ibas/ibas_acs_web.cgi
The light curves, binned at 50 ms, are derived from 91 independent
detectors with different lower energy thresholds (mainly between 80 keV
and 150 keV) and an upper threshold at about 100 MeV. The ACS response
varies as a function of the GRB incident angle. For these reasons we
caution that the count rates cannot be easily translated into physical
flux units. It is not possible to localize a burst based on the SPI-ACS
data.
GCN Circular #11893
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 exceptionally bright GRB 110106A, (Savchenko et al., GCN 11890)
triggered Konus-Wind at T0=3D13446.671s UT (03:44:06.671)
The burst light curve consists of a single FRED-like pulse,
the total duration of the burst is ~8 s.
The emission is seen up to ~10 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB110406_T13446/
The non-zero spectral lag between the Konus-Wind light curves
is evident, the following values are obtained:
-------------------------------------------------------------
LC1(keV) LC2(keV) Search interval(s) Scale Lag(ms)
-------------------------------------------------------------
G2(70-300) G1(18-70) -0.048:+2.016 16 ms +58 =B1 6
G3(300-1160) G1(18-70) -0.016:+1.968 16 ms +127 =B1 6
G3(300-1160) G2(70-300) -0.048:+2.016 16 ms +64 =B1 5
-------------------------------------------------------------
As observed by Konus-Wind the burst
had a fluence of (4.8 =B1 0.5)x10-5 erg/cm2,
and a 16-ms peak flux, measured from T0+0.160s,
of (1.5 =B1 0.1)x10-4 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum of the burst
(from T0 to T0+9.216 s) can be fitted
in the 20 keV - 10 MeV range by the GRB (Band)
model, for which:
the low-energy photon index alpha =3D -1.24 (-0.07, +0.08),
the high energy photon index beta =3D -2.30 (-0.25, +0.15),
the peak energy Ep =3D 326(-42, +49) keV,
chi2 =3D 117/89 dof.
The spectrum at the maximum count rate
(measured from T0+0.064 to T0+0.256 s) is best fit
in the 20 keV - 10 MeV range by the GRB (Band)
model, for which:
the low-energy photon index alpha =3D -0.61 (-0.13, +0.15),
the high energy photon index beta =3D -2.05 (-0.12, +0.10),
the peak energy Ep =3D 417(-64, +77) keV,
chi2 =3D 56.5/56 dof.
All the quoted results are preliminary.
The lag errors are given on 1 sigma level.
All other quoted errors are at the 90% confidence level.
GCN Circular #11900
K. Hurley on behalf of the Mars Odyssey and MESSENGER GRB teams,
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. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks,
D. Svinkin, and T. Cline on behalf of the Konus-Wind team,
D. M. Smith, R. P. Lin, J. McTiernan, R. Schwartz, W.
Hajdas, and A. Zehnder, on behalf of the RHESSI GRB 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,
S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of
the Swift-BAT team, and
J. Goldsten, on behalf of the MESSENGER NS GRB team, report:
The bright GRB110406A (GCN 11890, 11893), was detected by Mars Odyssey
(HEND), MESSENGER (GRNS), Konus-Wind, INTEGRAL SPI-ACS, Suzaku WAM,
RHESSI, and Swift BAT (outside the coded field of view). We have
triangulated it to a preliminary, 3 sigma confidence error box whose
corners are:
RA(2000) DEC(2000)
17.008898= 1 h 8 m 2.14 s 36.015742= 36 o 0 ' 56.67 "
16.578396= 1 h 6 m 18.82 s 35.984576= 35 o 59 ' 4.48 "
18.141649= 1 h 12 m 34.00 s 35.601842= 35 o 36 ' 6.63 "
17.702525= 1 h 10 m 48.61 s 35.586179= 35 o 35 ' 10.24 "
The best-fit position is RA, Dec= 17.340, +35.809. The error
box area is ~600 sq. arcmin.
Due to its proximity to the Sun, this position cannot be observed
by Swift.
This error box can be improved.
GCN Circular #11909
A. Rowlinson, P.T. O'Brien, N.R. Tanvir (U. Leicester) and A.J. Levan
(U. Warwick) report:
We note that the the error box of the bright short hard GRB 110406A
detected by INTEGRAL SPI-ACS and the IPN (GCNs 11890, 11893, 11900)
overlies NGC 404, a dwarf galaxy at a distance of ~3 Mpc. The IPN
error box and the extent of NGC 404 are overlayed on a GALEX FUV image
here: http://www.star.le.ac.uk/~bar7/NGC404_FUV.jpg
NGC 404 is a recently rejuvinated lenticular galaxy, forming the
majority of its new stars in a ring with a star formation rate of
2.5e-3 M_sol yr^-1 (Thilker et al., 2010, ApJ, 714, L171).
If this GRB is associated with NGC 404, the isotropic energy released
would be ~6e46 erg (20 keV - 10 MeV) using the Konus-Wind spectral fit
(GCN 11893) which would be consistent with an SGR giant flare origin,
while the presence of a young stellar population within this galaxy
would also be consistent with this model. For comparison, the giant
flare from SGR 1806-20 had Eiso ~3.7e46 erg (Hurley et al., 2005,
Nature, 434, 1098).
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