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TITLE:   GCN CIRCULAR
NUMBER:  11278
SUBJECT: GRB 100915B: a long GRB detected by INTEGRAL
DATE:    10/09/15 07:19:49 GMT
FROM:    Sandro Mereghetti at IASF/CNR  <sandro@iasf-milano.inaf.it>

S.Mereghetti, A.Paizis (IASF- Milano), D.Gotz (CEA-Saclay), E. Bozzo, 
A.Taylor, M. Beck (ISDC, Versoix), and J. Borkowski (CAMK, Torun) on 
behalf of the IBAS Localization Team report:

a gamma ray burst lasting about 4 s has been detected by IBAS in the 
IBIS/ISGRI data at 05:49:39 U.T. on September 15th.

Its refined coordinates (J2000) are:
RA=  85.3944 (deg) 
DEC=+25.0949 (deg)

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

A preliminary analysis gives a   20-200 keV fluence of about  3e-7 
erg/cm2 and a peak flux of about 1 ph/cm2 s  (1 s integration time)

A plot of the light curve will be posted at

http://ibas.iasf-milano.inaf.it/IBAS_Results.html

This message can be cited.

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TITLE:   GCN CIRCULAR
NUMBER:  11284
SUBJECT: GRB 100915B: Fermi GBM observation
DATE:    10/09/15 20:52:50 GMT
FROM:    Sheila McBreen at MPE  <smcbreen@mpe.mpg.de>

Sheila McBreen (UCD/MPE)
reports on behalf of the Fermi GBM Team:

"At 05:49:39.62 UT on 15 Sept 2010, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 100915B (trigger 306222581 / 100915243)
which was also detected by INTEGRAL/IBIS (Mereghetti et al. 2010, GCN
11278). The GBM on-ground location is consistent with the INTEGRAL
position.
The angle from the Fermi LAT boresight is 125 degrees.

The GBM light curve consists of one pulse
with a duration (T90) of 7.8 (+/- 0.7) s (50-300 keV).
The time-averaged spectrum from T0-5.6 s to T0+3.6 s is
adequately fit by a power law function with an exponential
high energy cutoff.  The power law index is 1.35 (+1.63/- 1.10) and
the cutoff energy, parameterized as Epeak, is 83.49 (+ 14.50/-9.81) keV
(CSTAT 273 for 243 d.o.f.).

The event fluence (10-1000 keV) in this time interval is
(4.82 +/- 0.06)E-07 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-2.56 s in the 10-1000 keV band
is 1.85 +/- 0.19 ph/s/cm^2.

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



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TITLE:   GCN CIRCULAR
NUMBER:  11286
SUBJECT: GRB 100915B: GRT Optical Observation
DATE:    10/09/16 00:15:23 GMT
FROM:    Takanori Sakamoto at NASA/GSFC  <takanori.sakamoto-1@nasa.gov>

T. Sakamoto (UMBC/GSFC), D. Donato (UMCP/GSFC), N. Gehrels (GSFC),
T. Okajima (JHU/GSFC), Y. Urata (NCU), C.A. Wallace (FGCU)

We observed the field of GRB 100915B detected by INTEGRAL 
(trigger #6061; Mereghetti et al., GCN Circ. 11278) with the 14-inch
Goddard Robotic Telescope (GRT) located at the Goddard Geophysical
and Astronomical Observatory (http://cddisa.gsfc.nasa.gov/ggao/).

A total 226 images (excluding the bad quality images) of 5 sec (200 images) 
and 30 sec (26 images) exposures were taken in the R filter starting from 
September 15 05:50:55 (UT) about 76 seconds after the trigger (62 seconds 
after the initial INTEGRAL position notice) and stopped on 
September 15 06:37:44 (UT).  The weather condition was relatively poor 
during the observation.  We do not detect the optical afterglow both in 
the individual images and the stacked image inside the INTEGRAL position 
(Mereghetti et al., GCN #11278).  The estimated five sigma upper limit 
of the combined image (total exposure of 1740 sec) is ~17.7 mag using 
the USNO-B1 catalog.