A soft (E≲2 keV) excess over the power-law component dominant at higher energies has been found in the X-ray spectra of many Seyfert galaxies. The origin of the soft excess is still an open issue. In the past it was often associated with the high-energy tail of the thermal emission of the accretion disk, but it has been shown recently that the temperature of the disk should be constant (0.1–0.2 keV), regardless of the mass and luminosity of the AGN (Gierlinski & Done 2004). This result implies that some other mechanism is at work, as the temperature of the disk should depend on both the mass of the black hole and the accretion rate.

IGR J17252–3616 is the hard X-ray counterpart of EXO 1722–363. The regular monitoring by INTEGRAL shows that IGR J17252–3616 is a persistent source with an average count rate of $\sim$6.4 mCrab in the 20–60 keV energy band. A follow-up observation with XMM-Newton showed that the source is located at R.A. (2000.0) $=17^{h}25^{m}11.4^{s}$ and Dec. $=-36{\hbox{$^\circ$}} 16 {\hbox{$^\prime$}} 58.6 \hbox{$^{\prime\prime}$}$ with an uncertainty of $4 \hbox{$^{\prime\prime}$}.

The source is a binary X-ray pulsar with a spin period of 413.7 s. The spectral shape is typical for an accreting pulsar except that a huge intrinsic absorption and a cold iron fluorescence line are detected. The absorbing column density and cold iron line do not vary with the pulse period. The observations suggest that the source is a wind-fed accreting pulsar accompanied by a supergiant star.

The ESA observatory INTEGRAL (International Gamma-Ray Astrophysics Laboratory) is dedicated to fine imaging and spectroscopy in the energy range 15 keV to 10 Mev with concurrent X-ray (3-35 keV) and optical monitoring. It was launched on October 17, 2002 and has been succesfully operating ever since. Its two main instruments the spectrometer SPI – optimized for high resolution spectroscopy – and the imager IBIS – optimized for for high resolution imaging – are complemented by the X-ray monitor JEM-X and the optical monitor OMC. All the high energy instruments use coded mask techniques, allowing imaging in the gamma-ray range and combining wide fields of view with high spatial resolution. The presentation gives an overview of the unique properties of INTEGRAL.

An analysis of the high-energy emission from IGR J16393–4643 is presented using data from INTEGRAL and XMM-Newton. The source is persistent in the 20–40 keV band at an average flux of $5.1\times10^{-11}$ergs cm$^{-2}$ s$^{-1}$, with variations in intensity by at least an order of magnitude. A pulse period of 912$\,{\pm}\,$3 s was discovered in the ISGRI and EPIC light curves. The source spectrum is a strongly-absorbed ($N_{\mathrm{H}}=(2.5\,{\pm}\,0.2)\times10^{23}$ cm$^{-2}$) power law that features a high-energy cutoff above 15 keV. Two iron emission lines at 6.4 and 7.1 keV, an iron absorption edge $\gtrsim$7.1 keV, and a soft excess emission of $7\times10^{-15}$ergs cm$^{-2}$ s$^{-1}$ between 0.5–2 keV, are detected in the EPIC spectrum. The shape of the spectrum does not change with the pulse. Its persistence, pulsation, and spectrum place IGR J16393–4643 among the class of heavily-absorbed HMXBs. The improved position from EPIC is R.A. (J2000)$=16^{\mathrm{h}}39^{\mathrm{m}}05.4^{\mathrm{s}}$ and Dec.$=-46^{\circ}42'12''$ ($4''$ uncertainty) which is compatible with that of 2MASS J16390535–4642137.

3C 273 is one of the brightest and best studied quasars. It has been observed for 770 ks with the imager IBIS (FoV 12 deg) on board INTEGRAL. To achieve the best possible S/N the dataset has been screened using several criteria indicating the quality of the data (i.e., number of good time intervals, etc). We describe the necessary tools and methods to analyze data of deep fields.

We present ground-based data of the BL Lac object PKS 2155-305 obtained during a large international campaign spanning the electro–magnetic spectrum from the radio waves to X-rays in November 1991. For the complete description of the observations and data analysis we refer to the paper by Courvoisier et al. 1993, and references therein. The ground-based data include radio, infrared JHKL and UBVRI fluxes as well as optical and near IR polarimetry.

The broad-band optical and near IR data from U to I exhibit the same behaviour in all bands: the flux nearly doubled over the well-covered period of 23 days. The cross-correlation function does not reveal any significant changes in the light-curves. Though significant variations in 24 hours have been recorded, the cumulated Fourier power spectrum drops to the noise level for periods shorter than 2.5 days. The spectral index remained constant.

The polarised flux varied by a larger factor than the total flux and did not follow the same pattern. The degree of polarisation and polarisation angle are nearly independent of the wavelength and are strongly correlated in all filters.

In the radio domain the spectral index increased from −0.1 on November 5 to +0.02 on 25-th.

The absence of the lag between the optical and infrared bands and the polarisation variations are consistent with a model in which the variability is caused by micro-lensing of the source (Stickel, Fried and Kühr 1988). One would, however, expect in this model that the variation in the polarisation and the total flux are tightly correlated contrary to what is observed.

The constant shape of the continuum spectral energy suggests that only the number of electrons whose emission is beamed towards the observer changes, rather than the arrival of fresh electrons that are being accelerated.

The variability of the polarisation may be explained by changes in the geometry of the magnetic field (dominant direction). This is consistent with the observed variations of the polarisation angle.

Several points indicate that extragalactic jets can interact with dense gaseous obstacles which occur on their ways. Examples of these interactions are the knotty structure of the radio and optical jet in M 87 and in other objects. These observations have been interpreted by Blandford & Königl in terms of collision of a jet with supernova remnants. We have reanalysed this idea taking into account new observations and improvements in the theory of diffusive shock acceleration. We find that the model requires a very high supernova birthrate (∼ 1 SN/year), which is not observed. It is more probable that the “obstacles” are formed by the stellar winds from the red giants. We estimate that the value of the magnetic field is ∼ 10−5 G in the interaction region (r=1kpc) (paper in preparation).

Simultaneous observations of 8 Seyfert 1 type AGN (Fairall-9, Mrk 590, NGC 4051, 3C 273, NGC 5548, Mrk 841, Q 1821+643 and 3C 390.3) obtained with ROSAT and IUE (RIASS program), and for 5 sources (Fairall-9, NGC 4051, 3C 273, Mrk 841 and Q 1821+643) with Ginga, have been analysed with the aim of describing the UV to soft X-ray spectral component in these sources.

The IUE-ULDA database (Version 3.0, complete until the end of 1988) contains about 3500 spectra of more than 500 AGN of different classes (see Courvoisier and Paltani, IUE-ULDA Access Guide No. 4 A & B, ESA SP 1153 A & B 1992). We selected 67 objects for which the variability properties could be investigated. For each object we estimated the amplitude of the variability by means of the standard deviation σ(λ) of the flux at different frequencies divided by the mean flux.

From June 15 to 28, 1991 the Compton Gamma-Ray Observatory (CGRO) observed the radio-loud quasar 3C 273. All four CGRO instruments detected radiation from this quasar in their relevant energy range (from 20 keV to 5 GeV). Simultaneous and quasi-simultaneous observations (spanning the time period May 27 – July 25, 1991) by instruments sensitive at other wavelengths have also been obtained. The data from all these observations spanning the frequency range from ∼ 109 Hz to ∼ 1026 Hz were collected and analysed. The resulting energy-density spectrum is shown in the figure below. It shows two maxima, one in the UV, another one at low-energy γ-rays which have nearly the same strength (the corresponding luminosities per decade of frequency for H0 = 60(km/s)/Mpc are 3.2·1046 erg/s and 2.7·1046 erg/s, respectively). A break of the spectrum at low-energy γ-rays is evident. From a detailed analysis a break energy of (2±1.5) MeV could be derived corresponding to a frequency of (4.8±3.6)·1020 Hz. The observed spectral break between X- and γ-rays is ∼ 0.8, much higher than the value of 0.5 predicted by some models. A more detailed paper on this topic is in preparation (Lichti et al.).