GRB 150912A

S.Mereghetti (IASF-Milano), D.Gotz (CEA, Saclay), E.Bozzo, C.Ferrigno, 
L.Ducci (ISDC, Versoix), and J.Borkowski (CAMK, Torun) on behalf of the 
IBAS Localization Team report:

a gamma ray burst lasting about 30 s has been detected by IBAS in the 
IBIS/ISGRI data at 10:37:30 UT of 2015 September 12.

The refined coordinates (J2000) are:

R.A.= 248.4435 deg
DEC.= -21.03376  deg

with an uncertainty of   2  arcmin (90% c.l.).

The burst had a peak flux of about 1.5 counts/cm2/s (20-200 keV, 1-s 
integration time) and a fluence in the same energy range of about 1e-6 
erg/cmq.

A plot of the light curve will  be posted at
http://ibas.iasf-milano.inaf.it/IBAS_Results.html

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the INTEGRAL GRB 150912A. 
Automated analysis of the XRT data will be presented online at
http://www.swift.ac.uk/ToO_GRBs/00020557

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the INTEGRAL event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

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

E. Bissaldi (INFN Bari) reports on behalf of the Fermi GBM Team:


"At 10:37:38.70 UT on 12 September 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 150912A (trigger 463747062/150912443),
which was also detected by INTEGRAL (Mereghetti et al. 2015, GCN 18291
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 ).
The GBM on-ground location is consistent with the INTEGRAL position.

The angle from the Fermi-LAT boresight at the GBM trigger time is 67 degrees.

The GBM light curve consists of a single peak
with a duration (T90) of about 30 s (50-300 keV).
The time-averaged spectrum from T0-6 s to T0+22 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.11 +/- 0.10 and
the cutoff energy, parameterized as Epeak, is 250 +/- 40 keV.

The event fluence (10-1000 keV) in this time interval is
(4.5 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux, measured
starting from T0+2.2 s in the 10-1000 keV band,
is 2.82 +/- 0.25 ph/s/cm^2.


The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias

V. Lipunov, E. Gorbovskoy,  N.Tyurina, V.Kornilov,
P.Balanutsa, A.Kuznetsov, D.Kuvshinov, E.Popova
Lomonosov Moscow State University, Sternberg Astronomical Institute

K.Ivanov, O.Gres, N.M.Budnev, S.Yazev,
Irkutsk State University

D.Buckley, S. Potter, A.Kniazev, M.Kotze
South African Astronomical Observatory

A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov, A.Gabovich
Blagoveschensk Educational State University, Blagoveschensk

V.Krushinski, I.Zalozhnih
Ural Federal University, Kourovka

Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

Claudio Mallamaci, Carlos Lopez and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in IAC  was pointed to the  GRB150912A 33865 sec (9.4 h) after 
trigger time at 2015-09-12 20:01:55 UT directly after the sunset. On our 
first single and coadd sets we haven`t found optical transient  within IPN 
error-box (Mereghetti et. al GCN 18291
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 ).
The 5-sigma upper limit has been about 19.2 on single (180 sec) and ~ 20.3 
at coadd (10x180 sec) images.
The message may be cited.

D. Kuroda (OAO, NAOJ),  H. Hanayama, T. Miyaji, J. Watanabe (IAO, NAOJ),
K. Yanagisawa (OAO, NAOJ), S.Nagayama (NAOJ), M. Yoshida (Hiroshima),
K. Ohta (Kyoto) and N. Kawai(Tokyo Tech)
report on behalf of the MITSuME and OISTER collaboration:

We observed the field of GRB 150912A (Mereghetti et al., GCNC 18291)
with the optical three color (g', Rc and Ic) CCD camera attached
to the Murikabushi 1m telescope of Ishigakijima Astronomical
Observatory.

The observation started on 2015-09-12 12:15:39 UT (~1.6 h after the burst).
We did not find any new point source within the INTEGRAL-IBAS error circle
(Mereghetti et al., GCNC 18291) in all the three bands.

Three sigma upper limits of the OT are listed below.
We used GSC2.3 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'     Rc     Ic
-----------------------------------------------------
0.07014    12:18:30     300.0   >19.7  >19.4  >18.6
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]

K.L. Page (U. Leicester), M. H. Siegel (PSU) and P.A. Evans (U.
Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the INTEGRAL-detected
burst GRB 150912A (Mereghetti et al. GCN Circ. 18291
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 ), collecting 4.7
ks of Photon Counting (PC) mode data between T0+32.6 ks and T0+50.4 ks.


No X-ray sources have been detected inside or close to the INTEGRAL
error region. The 3-sigma upper limit in the field ranges from ~0.002
to ~0.004 ct s^-1, corresponding to a 0.3-10 keV observed flux of
9.0e-14 to 1.5e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum).

Two uncatalogued sources were detected too far from the GRB position to
be likely afterglow candidates.

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
http://www.swift.ac.uk/ToO_GRBs/00020557.

Swift-UVOT also began settled observations of the field of GRB 150912A
32.6 ks after the INTEGRAL trigger. No optical afterglow consistent
with the INTEGRAL position is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial
exposures are:

Filter	       T_start(s)   T_stop(s)	   Exp(s)	  Mag

w2		 32643	      50446	    4789	 >21.2

The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.42 in the direction of
the burst (Schlegel et al. 1998).

This circular is an official product of the Swift-XRT and UVOT teams.