Active Galactic Nuclei emit a substantial portion of their bolometric luminosities in X-rays. For example, the knots in radio jets are prominent sources of synchrotron X-rays while the hotspots of the brightest FRIIs emit self-synchrotron or Inverse Compton radiation. Most high-energy studies on flat-spectrum radio sources have been conducted for blazars which are dominant at $\gamma$-rays.

Augusto et al. (1998) have built a sample of 55 flat-spectrum radio sources dominated by structures (knots, hotspots, etc.) $\sim$0.1–2 kpc away from the nucleus. Seventeen (31%) of these are detected in X-rays (they tend to be the radio strongest) evenly splitting, morphologically, both at optical (radio) bands: nine QSO/BLLac (core-jets) on one-side; eight Galaxy/Sy2 (CSO/MSO/FRII) on the other. We have identified five confirmed compact/medium symmetric objects (CSO/MSOs) as X-ray emitters. A comparable type of source to CSO/MSOs is the physically similar (1–15 kpc) compact steep spectrum source (CSS), 28/129 (22%) of which are detected in X-rays, from a literature-selected sample (the percentage is smaller than for the 55-source sample due to a lower $<\!\!S_{4.85}\!\!>$). A 95% conf. level relation is found for CSSs: $S_X \propto (S_{4.85})^{0.6}$ and we found undistinguishable radio/X-ray properties for both the 55-source and CSS samples: clearly, their similar morphologies (e.g. knots in jets) stand up stronger than their radical radio spectrum differences.

Only two sources among the 55 (4%) have $\gamma$-ray detections and they seem quite abnormal (in $\alpha_{x\gamma}$ values, at least)–one of them is in a Sy2, not in a blazar.

We have used Chandra archival observations of 19 galaxies hosting LINERs to explore the morphology and source population of their inner kiloparsec. Our goal was, in general, to determine the power source behind their nuclear X-ray emission and, in particular, to investigate the presence of an AGN. We find an AGN in 12 of the 19 galaxies in the sample. We also find that diffuse, thermal emission is common with properties very similar to what is found in normal galaxies. In 10 out of the 19 galaxies, the diffuce emission dominates the nuclear X-ray power. The X-ray point-source populations were studied by producing cumulative luminosity functions and their properties are also similar to what is found in normal galaxies.

We refer on analysis of the ESA INTEGRAL satellite data for blazars, promising sources to be observed during their active states. We further refer on searches for and analysis of supermassive binary black holes requiring very long time intervals (50 years and more) provided by digitised astronomical plates.

Low-frequency ($f \leq 10^{-6}$ Hz) quasi-periodic variability observed from radioloud, jet-emitting Active Galactic Nuclei (AGNs) can provide substantial inductive support for the presence of close ($d \lesssim 0.1$ pc) supermassive binary black holes in their centers. Such periodic variability may arise, for example, due to differential Doppler boosting along helical jet paths driven by the orbital motion or jet precession. If the jet path is non-ballistic, travel time effects can lead to a strong reduction of the observable period by up to a factor of $\gamma_b^{-2}$. Here we suggest a binary model where the optical periodicity with timescale of several years is related to accretion disk interactions, radio periodicity to Newtonian jet precession and periodicities in the high energy bands to the orbital motion of the jet. We analyze the explanatory potential of such a framework and comment on the possible origin of periodicities in AO 0235+16.

XMM-Newton has observed the quasar 3C273 several times between 2000 June and 2005 July. In addition data of NASA's Rossi X-ray Timing Explorer is used. We present the results of this monitoring campaign.

The X-ray spectrum of 3C273, in the energy regime of 0.2–100 keV, is believed to be composed of three components: a power law component above about 3 keV, a soft excess below about 2 keV, and an Fe-line. The Fe-line, detected in only a few observations of 3C273, is not detected significantly in individual XMM-observations. Only the 2000 June observations show evidence for a presence of a broad line feature. The high energy component above 3 keV is well described by a single power law model with varying indices and fluxes. The steeper spectra show significantly higher flux levels. The soft excess component below 2 keV also shows variations in flux and spectral slope. Different models are tested to identify the soft excess to be thermal or non-thermal emission.

The association of “long” Gamma-Ray Bursts (durations > 2 seconds) with peculiar Type Ic supernovae suggests strongly that this type of GRB is produced by the collapse of the rapidly rotating core of an initially very massive star to a black hole. At the time of collapse the star has lost its hydrogen-rich envelope and the GRB is thought to be produced by a collimated relativistic jet of matter ejected along the star's rotation axis. The angular momentum constraints for producing such a “collapsar” or “hypernova” suggest that the GRB-producing core collapses constitute only a small fraction of all core collapses of massive stars. As to the short-duration GRBs (< 2 seconds), which make up about one third of all GRBs, the most favoured model is that of the coalescence of a double neutron star or of a neutron star-black hole binary. Also these events are expected to be very rare, having a frequency of at most one event per hundred thousand years for a galaxy like our own. Due to the collimation of the relativistically ejected matter, the observable frequency of GRB events will, like in the case of the “long” bursts, be at least a factor hundred smaller.

The results obtained during the first three years of operation of INTEGRAL will be reviewed. Over 30 GRBs have been localised by the INTEGRAL burst alert system (IBAS) and the coordinates distributed. The follow-up observations with XMM-Newton and large telescopes have led to many interesting results. A comparison will also be made between the sensitivities of INTEGRAL and SWIFT.

The particle acceleration and the non-thermal radiation in the magnetospheres of collapsing stars are considered. The collapsing stars can be powerful sources of the high-energy charged particles and the non-thermal radiation bursts. These bursts can be observed by means of modern astronomical instruments.

Recent observations have suggested that the true energy release of GRBs is potentially far less than previously thought. This is due to beaming, a signature of which is a broadband break in the power-law decay of the afterglow emission. Taking these results we have constructed a basic distance estimator, which may be useful as a diagnostic tool for the large amount of GRBs without a spectroscopically measured redshift.

REM is a fast slewing automatic telescope dedicated to the prompt observation of GRB afterglows. The telescope automatically reacts to GCN alerts, beginning follow-up observations in both infra-red and optical wavelengths. Recent observations of GRBs have shown the capabilities of REM to begin follow up observation in the order of 10s of seconds after the burst.

We present gamma–ray and X-ray analysis of GRB040223 observed by INTEGRAL and XMM-Newton. GRB 040223 has a peak flux of $(1.6 \pm 0.1) \times 10^{-8}$ ergs cm$^{-2}$ s$^{-1}$, a fluence of (4.4 $\pm$ 0.4) $\times$ 10$^{-7}$ ergs cm$^{-2}$ and a steep photon power law index of −2.3 $\pm$ 0.2, in the energy range 20–200 keV. The steep spectrum implies that it is an X-ray rich GRB with emission up to 200 keV and $E_{\rm peak}<20$ keV. The luminosity-lag relationship was used to obtain a redshift $z=0.10^{+0.04}_{-0.02}$. The isotropic energy radiated in $\gamma$-rays and X-ray luminosity after 10 hours are both orders of magnitude less than classical GRBs.

This talk reviews the observations of the high-energy emission of young supernovae, providing an update from previous reviews in 1995 and 2003. A summary plot shows the number distribution of X-ray luminosities, currently totalling 25 supernovae, from which it is clear that SN IIP are weak X-ray sources, SN IIn are very luminous sources, and SN Ib/c cover a broad range in luminosity.

Owing to the rapid progress of space sciences and the high-energy astrophysics in the past 2–3 decades, historical supernova records have made important contributions to modern astrophysics and will continue to do so in the future. The main topics here are the earliest supernova observed by human beings and the AD393 guest star as well as our new concept of “Po stars”

The supernova explosion of 1054 AD, which originated the Crab Nebula and Pulsar, is probably the astronomical event which has been most deeply studied by means of historical sources. However, many mysteries and inconsistencies, both among the different sources and between what is deduced by the historical records and the present day astronomical data, are demanding extraordinary efforts by theoretical astrophysicists in order to put all the data in a meaningful framework. An accurate analysis of the historical sources, like the one we are presenting here, may contribute to solve some of these problems.

We have collected from the literature X-ray fluxes of Young Supernovae, measured with various instruments. After converting the data to one energy range, we have compared the X-ray light curves of these objects. The X-ray luminosities of early Supernovae show coherent trends with Supernova type and provide significant, though short-lived contributions to the X-ray luminosity of Starbursts.

ULXs have been studied for 20 years, but only recently have detailed X-ray spectral/timing studies, and investigations of their statistical properties and their environments and counterparts been undertaken. I will review progress in these areas.

We suggest that the ultraluminous X-ray sources located in external galaxies (ULXs) are supercritical accretion disks like that in SS433, observed close to the disk axis. We estimate parameters of the SS433 funnel, where the relativistic jets are formed. Emergent X-ray spectrum in the proposed model of the multicolor funnel (MCF) is calculated. The spectrum can be compared with those of ULXs. We predict a complex absorption-line spectrum with broad and shallow K$\alpha$/Kc blends of the most abundant heavy elements and particular temporal variability. Another critical idea comes from observations of nebulae around the ULXs. We present results of 3D-spectroscopy of nebulae of two ULXs located in Holmberg II and NGC6946. In both cases the nebula is found to be powered by the central black hole. The nebulae are compared with SS433 nebula (W50).

Chandra and XMM-Newton improve our understanding of X-ray populations in galaxies. In particular, there exists a class of ultra-luminous X-ray sources (ULXs) for which the observed luminosity is greater than $10^{39}$ ergs s$^{-1}$. ULXs are of great interest since they represent a population of possible intermediate-mass black holes. While the spectra of majority of ULXs are similar to Galactic X-ray binaries, a few ULXs have very soft X-ray emission ($kT=50$–100 eV) resembling supersoft X-ray sources (SSSs) discovered in the Milky Way and the Magellanic Clouds. We here report some recent multiwavelength observations of three ultra-luminous SSSs in M101, NGC 300, and the Antennae. They have shown many interesting behaviors such as state transitions, spectral changes, and time variabilities in different timescales. Unlike typical SSSs, ultra-luminous SSSs are unlikely associated with white dwarfs because of the high X-ray luminosities. We discuss some binary models involving stellar-mass and intermediate-mass black holes to explain the nature of the systems.

In a subset of the most luminous of the so-called “ultra-luminous” X-ray sources in nearby galaxies, there is evidence for black holes with masses considerably higher than found in Galactic binaries. Apart from extremely high X-ray luminosities, cool disks found in the X-ray spectra of these sources and X-ray timing measurements form the basis for present evidence for intermediate-mass black holes in these sources. New optical and radio measurements appear to support the X-ray evidence. I will review recent X-ray, optical, and radio observations of these ULXs, and discuss the strengths of the intermediate-mass black hole interpretation, arguments against this interpretation, and future prospects for revealing the nature of these ULXS more clearly.

The central controversy over whether or not ultraluminous X-ray sources (ULXs) contain a new “intermediate-mass” class of black holes (IMBHs) remains essentially unresolved. Indeed, whilst many recent X-ray spectroscopy results find evidence for a cool (100–200 eV) accretion disc – the expected signature of a ${\sim} 1000$ M$_{\odot}$ IMBH – in ULX spectra, most of the circumstantial evidence (a combination of multiwavelength counterparts, theoretical modelling and the behaviour of accreting black holes in our own Galaxy) argues that the black holes underlying ULXs could be substantially less massive. I will present a new analysis of the deepest XMM-Newton observations of ULXs that directly addresses their underlying nature. This includes the results of a new 100-ks observation of the archetypal ULX Holmberg II X-1. Though a slight soft excess in its X-ray spectrum can be fitted by a cool accretion disc model, a rigorous analysis of the temporal data shows that the black hole cannot be larger than ${\sim}100$ M$_{\odot}$. Interestingly, we find evidence that the putative accretion disc corona is cool and optically thick in this source, unlike most Galactic binaries. We have also undertaken a detailed spectral analysis of the next 12 best ULX datasets in the XMM-Newton archive. Using physically self-consistent spectral modelling we show that whilst all the ULXs show possible cool accretion discs, the majority of these ULXs appear dominated by an optically-thick Comptonising medium. I will argue that this is evidence that most (though not necessarily all) ULXs contain black holes that are at most a few tens of solar masses in size.