The Bright Quasar 3C 273

We review the observed properties of the bright quasar 3C~273 and discuss the implications of these observations for the emission processes and in view of gaining a more global understanding of the object. Continuum and line emission are discussed. The emission from the radio domain to gamma rays are reviewed. Emphasis is given to variability studies across the spectrum as a means to gain some understanding on the relationships between the emission components. 3C~273 has a small scale jet and a large scale jet. The properties of these jets are described. It is also attempted to relate the activity in the small scale jet to that observed in the radio and infrared continuum.Comment: 47 pages, 12 figures. to appear in Astronomy and Astrophysics revie

Astronomy, space science and geopolitics

Astronomy has played a major part in the development of civilisations, not only through conceptual developments, but most importantly through the very practical gains obtained through the observation of Sun, Moon planets and stars. Space sciences, including astronomy, have also played a major rôle in the development of modern societies, as an engine for most subsequent space technology developments. Present trends tend to decrease the rôle of science in space development. This trend should be reversed to give modern "societies” their independence in space-related matters that permeate the lives of all inhabitants of the Eart

What May We Learn from Multi-wavelength Observations of Active Galactic Nuclei

We discuss how several of the questions that remain unclear on the physics of Active Galactic Nuclei may find elements of answers when using in the coming years the extraordinary set of instruments that will be flying simultaneously to observe in all bands of the electromagnetic spectrum. The choice of questions mentioned here is personal and not exhaustive.Comment: 10 pages, no figures, to appear in "Quasars, AGNs and related research across 2000", Rome May 200

Surprises in the Hard X-ray Sky

Cosmic objects emit throughout the electro-magnetic spectrum, from radio waves to very high-energy gamma rays. Some spectral regions can be observed from the ground, but space instrumentation is needed for most of them. Some spectral regions are particularly difficult, for example hard X-rays and MeV gamma rays. For one thing, in this spectral region photons interact least with matter. Moreover, no focussing optics was available until very recently. INTEGRAL, the gamma ray observatory mission led by ESA, was designed to observe the sky in this very domain

Ratio of energies radiated in the universe through accretive processes and nucleosynthesis

We present here a new determination of the ratio of energies radiated by active galactic nuclei and by stars and discuss the reasons for the apparently conflicting results found in previous studies. We conclude that the energy radiated by accretion processes onto super massive black holes is about 1 to 5% of the energy radiated by stars. We also estimate that the total mass accreted on average by a super massive black hole at the centre of a typical 10^11 Msol galaxy is of about 7 10^7 Msol.Comment: 6 pages, 2 figures, accepted by Astronomy & Astrophysic

Hard X-ray colours of Neutron Star and Black Hole Low Mass X-ray Binaries with INTEGRAL

The X-ray spectra of Low Mass X-ray Binaries (LMXB) can change on short time-scales, making it difficult to follow their spectral characteristics in detail through model fitting. Colour-colour (C-C) diagrams are therefore often used as alternative, model independent, tools to study the spectral variability of these sources. The INTEGRAL mission, with its high sensitivity, large field of view and good angular resolution, is well suited to study the hard X-ray properties of LMXBs. In particular the ISGRI imager on board of INTEGRAL allows the regular monitoring of the sources in the less frequently studied domain above 20 keV. In this proceeding, C-C diagrams have been made with data from the INTEGRAL public archive; a search is made for systematic differences in the C-C diagrams between black hole candidates (BH) and neutron stars (NS) in LMXBs using a moments analysis method.Comment: Paper from poster presentation at COSPAR meeting, Beijing, 2006. in press: Advances in Space Research, Editor: Wynn H