GRB 091111

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

a long faint and soft gamma-ray burst has been detected by the  
INTEGRAL Burst Alert System in IBIS/ISGRI data on November 11 2009.  
Due to its faintness no automatic alert has been issued and the GRB  
has been identified through the routine off-line analysis of the low  
significance triggers. The GRB starts at 15:21:59 U.T. and lasts for  
about 100 s.

The GRB coordinates (J2000) are

R.A. : 137.8133 [degrees] ,  Dec.: -45.9093 [degrees]

with a 90% c.l. radius unercainty of 2.5 arcmin.

Even if no known X-ray source is present in the IBAS error circle, we  
note that the low galactic latitude of the object and its soft X-ray  
spectrum may indicate also a Galactic transient origin.
The light curve of the GRB will be posted at http://ibas.iasf-milano.inaf.it/IBAS_Results.html

This message can be cited.

[GCN OPS NOTE(12nov09):  Per author's request, CB was added
to the author list.]

J. Gorosabel (IAA-CSIC),  A. de Ugarte Postigo (INAF-OAB),  A.J.  
Castro-Tirado, M. Jelinek (IAA-CSIC), P. Kubanek (IPL UV, IAA-CSIC),  
R. Cunniffe, S. Guziy (IAA-CSIC), P. Yock  (Auckland Univ.), W.H.  
Allen (Vintage  Lane Obs.), I. Bond (Massey Univ.), G. Christie  
(Stardome Obs.), report on behalf of a larger collaboration, report:

"We have observed the field of the INTEGRAL GRB  091111 (Gotz et al.  
GCNC 10159) using the 0.6m Yock-Allen robotic telescope (BOOTES-3)  
located in Bleinheim, New  Zealand.  The observations were carried out  
between Nov. 12.45208 UT and 12.47379 UT, with a total exposure time  
of 88 min (starting 19.5 h after the burst).  Visual comparison with  
the DSS does not show any new source in our combined unfiltered image  
of the INTEGRAL error box down a limiting magnitude (3 sigma) of R~19.6.

Further observations are ongoing."

A.  de  Ugarte  Postigo (INAF-OAB), J.  Gorosabel,  A.J. Castro-Tirado,
M.  Jelinek (IAA-CSIC), P.  Kubanek (IPL UV, IAA-CSIC) and W.H. Allen
(Vintage  Lane Obs.), on behalf of a larger collaboration, report:

"During regular monitoring, the all-sky camera located at BOOTES-3
observatory in Blenheim, New Zealand observed the field of the
INTEGRAL GRB 091111 (Gotz et al. GCN 10159
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 ) before during and
after the burst onset. We have examined the images obtained at the
time of the GRB and we do not detect any new source within the
INTEGRAL error box. In the following table we give time ranges and
3-sigma limiting magnitudes of the observations that overlap with the
gamma-ray emission.

T-T0(start-->end)  Lim
=================
-31s --> +5s           9.3
+24s --> +60s        9.3
+79 --> +115s        9.3

This GCNC can be quoted."

V. Mangano, B. Sbarufatti (INAF-IASF PA),
H. A. Krimm (CRESST/GSFC/USRA) and D. M. Palmer (LANL)
report on behalf of the Swift-XRT team:

The INTEGRAL burst GRB091111 (Gotz et al. GCN Circ. 10159
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 )
has been observed by Swift on 2009 11 12 with a 5 ks ToO started
at 19:00 UT (trigger 020120).
We have analysed 5.4 ks of XRT data in PC mode, from 100361 s
to 115.3 ks after the INTEGRAL trigger.

An X-ray source is detected at
RA, Dec 137.82427, -45.92541 which is equivalent to:
   RA(J2000)  = 09h 11m 17.82s
   Dec(J2000) = -45d 55' 31.5"
with an uncertainty of 5.1 arcseconds (radius, 90% containment).

The light curve is probably decaying but more data are needed
to estimate the decay slope.

A spectrum formed from the PC mode data (30 counts within a
circular region of 15 pixel radius) can be fitted with an absorbed
power-law with a photon spectral index of 2.5 (+5, -3.4)
The best-fitting absorption column is < 5 x 10^22 cm-2, consistent
with the Galactic value of 6.2 x 10^21 cm-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 7.0 x 10^-11 (2.7 x 10^-10) erg
cm^-2 count^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00020120.

At the time of GRB 091111, the Swift/BAT was active, sensitive and pointing
such that the burst was in the BAT field of view with 25% mask coding.
There is no count rate increase detected in any of the four BAT energy bands

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

[GCN OPS NOTE(30dec12): In response to S.Mereghetti's communication,
this Subject-line was changed from "09111" to "091111".]