8th INTEGRAL Workshop: "The Restless Gamma-ray Universe"

Dublin, Ireland
2010 September 27–30

IGR J16318–4848: 7 years of INTEGRAL observations

Laura Barragán, Jörn Wilms, Ingo Kreykenbohm, Katja Pottschmidt, Manfred Hanke, Richard E. Rothschild, Felix Fürst

Since the discovery of IGR J16318-4848 in 2003 January, INTEGRAL has accumulated more than 5.8 Ms in IBIS/ISGRI. We present the first extensive analysis of the archival INTEGRAL data (IBIS/ISGRI and JEM-X when available) for this source, together with the observations carried out by XMM-Newton (2 in 2003 and 2 in 2004) and Suzaku (2006).
The source is very variable in the long-term, with periods of low activity, where the source is almost not detected, and flares with a luminosity 50 greater than its average value. IGR J16318-4848 a HMXB containing a sgB[e] star and a compact object (most probably a neutron star) deeply embedded in the stellar wind of the mass donor. The variability of the source can be ascribed to the wind of the optical star being very clumpy.
We also study the variation of the spectral parameters in time scales of INTEGRAL revolutions. The remarkable absorption linked to this source always gives a value for the NH around 1024 cm-2. During brighter phases the strong K-alpha iron line known from XMM-Newton and Suzaku observations is also detectable with the JEM-X instrument.


Cygnus X-1: shedding light on the spectral variability of the hard state of black holes

V. Grinberg, D.M. Marcu, K. Pottschmidt, M. Böck, J. Wilms M. Cadolle  Bel, A.M. Lohfink, F. Fürst, M. Hanke, M.A. Nowak, S. Markoff, A. Markowitz, J.A. Tomsick, J. Rodriguez, G.G. Pooley

We present an analysis of extensive recent monitoring observations of the black hole X-ray binary Cygnus X-1 (Cyg X-1) obtained as part of the 2007 to 2010 Cygnus Region Key Programme observations of the INTEGRAL mission. Cyg X-1 is one of only three persistent black hole binaries that spend most of their time in the hard spectral state. We concentrate on constraining the parameter range of the hard spectrum, a measurement that is typically difficult to obtain with high accuracy for transient sources, but which is important to know in order to understand the physics of the hot plasma of the jet base and/or the corona. While the hard X-ray spectrum of Cyg X-1 is one of the best studied examples of its kind, e.g., through our years long monitoring campaign with RXTE , the INTEGRAL monitoring allows us to study the spectral evolution from about half an hour over a few days to a few weeks, timescales that have been in part only sparsely sampled so far. After spending 3 years in the hardest regime of its parameter space, the source displayed a softening and flaring episode in mid 2009 and entered a soft state in spring/summer 2010. We compare X-ray broad band spectra (RXTE , INTEGRAL) of these two emission states. Furthermore, we use INTEGRAL/IBIS to extend the timing analysis with a resolution of up to 0.1 s to en- ergies above 20 keV.