Paper: astro-ph/0509117
Date: Tue, 6 Sep 2005 11:47:36 GMT (19kb)

Title: INTEGRAL three years later

Authors: L. Foschini, G. Di Cocco, G. Malaguti

Comments: 8 pages, no figures. Proceedings of the workshop "Science with the
New Generation of High-Energy Gamma-Ray Experiments", Cividale del Friuli
(Italy), 30 May - 1 June 2005. Invited talk
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The ESA INTErnational Gamma-Ray Astrophyisics Laboratory (INTEGRAL) is
composed of two main instruments (IBIS and SPI) for the gamma-ray astrophysics
(20 keV - 10 MeV), plus two monitors (JEM-X and OMC) for X-ray and optical
counterparts. It was launched on October 17th, 2002, from the Baikonur
cosmodrome (Kazakhstan) and it will be active at least up to 2008. A selection
of its main scientific contributions obtained to date are presented.

\\ ( http://arXiv.org/abs/astro-ph/0509117 , 19kb)

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Paper: astro-ph/0509123
Date: Tue, 6 Sep 2005 15:37:44 GMT (221kb)

Title: INTEGRAL observations of AGN in the Galactic Plane

Authors: S. Soldi, V. Beckmann, L. Bassani, T. J.-L. Courvoisier, R. Landi, A.
Malizia, A. J. Dean, A. De Rosa, A. C. Fabian, R. Walter

Comments: 12 pages, 12 figures, accepted for publication in A&A
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We present results on approximately one year of INTEGRAL observations of six
AGN detected during the regular scans of the Galactic Plane. The sample is
composed by five Seyfert 2 objects (MCG -05-23-16, NGC 4945, the Circinus
galaxy, NGC 6300, ESO 103-G35) and the radio galaxy Centaurus A. The continuum
emission of each of these sources is well represented by a highly absorbed (NH
> 1e22 1/cm^2) power law, with average spectral index Gamma = 1.9 +/- 0.3. A
high energy exponential cut-off at Ec ~ 50 keV is required to fit the spectrum
of the Circinus galaxy, whereas a lower limit of 130 keV has been found for NGC
4945 and no cut-off has been detected for NGC 6300 in the energy range covered
by these INTEGRAL data. The flux of Centaurus A was found to vary by a factor
of ~ 2 in 10 months, showing a spectral change between the high and low state,
which can be modelled equally well by a change in the absorption (NH from 17e22
to 33e22 1/cm^2) or by the presence of a cut-off at >~ 120 keV in the low state
spectrum. A comparison with recently reprocessed BeppoSAX/PDS data shows a
general agreement with INTEGRAL results. The high energy cut-off in the hard
X-ray spectra appears to be a common but not universal characteristic of
Seyfert 2 and to span a wide range of energies.

\\ ( http://arXiv.org/abs/astro-ph/0509123 , 221kb)

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Paper: astro-ph/0509133
Date: Tue, 6 Sep 2005 15:57:46 GMT (147kb)

Title: Outburst of the X-ray transient SAX J1818.6-1703 detected by INTEGRAL in
September 2003

Authors: S. A. Grebenev (1) and R. A. Sunyaev (1,2) (1 - Space Research
Institute, Moscow, 2 - Max-Planck-Institut fur Astrophysik, Garching)

Comments: 16 pages, 7 figures, to be published in Astronomy Letters, v. 31, n.
10, p. 672 (2005)
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During the observation of the Galactic-center field by the INTEGRAL
observatory on September 9, 2003, the IBIS/ISGRI gamma-ray telescope detected a
short (several-hours-long) intense (~380 mCrab at the peak) outburst of hard
radiation from the X-ray transient SAX J1818.6-1703. Previously, this source
was observed only once in 1998 during a similar short outburst. We present the
results of our localization, spectral and timing analyses of the object and
briefly discuss the possible causes of the outburst. The release time of the
bulk of the energy in such an outburst is appreciably shorter than the
accretion (viscous) time that characterizes the flow of matter through a
standard accretion disk.

\\ ( http://arXiv.org/abs/astro-ph/0509133 , 147kb)