Narrow Results

Suzaku is the fifth in the series of Japanese astronomy satellites devoted to observations of celestial X-ray sources launched on a Japanese M-V rocket on July 10, 2005. Suzaku features the excellent X-ray sensitivity, with high throughput over a broad-band energy range of 0.2 to 600 keV. Suzaku's broad bandpass, low background, and good CCD resolution makes it a unique tool capable of addressing a variety of outstanding problems in astrophysics.

Multiwavelength (MW) observations are an essential diagnostic tool to study the physics of blazars. Blazars, the most extreme objects among the Active Galactic Nuclei (AGNs), are characterized by rapid variability at all wavelengths from radio through TeV γ-rays. Considerable progress has been made in recent years thanks to multiwavelength monitoring campaigns. In this contribution, I will give a brief overview of the MW campaigns carried out in the past by large collaboration and their impact on the knowledge of the most important source/jet parameters needed by the physical models used to fit the observed blazar spectral energy distribution (SED). Furthermore, I will discuss some of the perspectives for multiwavelength observations during the operation of the gamma-ray mission GLAST.

MAGIC is presently the imaging atmospheric Cherenkov telescope with the largest reflecting surface and the lowest energy threshold. MAGIC concluded its first year of regular observation in April 2006. During this period and the preceding commissioning phase, 25 Active Galactic Nuclei have been observed and VHE γ-ray emission has been confirmed by 4 of them. Two more AGNs have been detected as γ-ray sources with high statistical significance for the first time. We report in this paper the results obtained analyzing data of the detected sources. Temporal and spectral properties of detected signals are shown and discussed.

Selected scientific highlights are presented from the first 5 years of observations of the gamma-ray sky by ESA's INTEGRAL space telescope. Its unprecedented angular resolution and sensitivity at high energies (≳ 20 keV) has allowed INTEGRAL to detect around 500 objects, many of which are new. Sources that have been classified are predominantly represented by active galactic nuclei (AGN) and X-ray binaries (XRBs) whereby a compact object (a supermassive black hole in AGN, usually a neutron star in XRBs) accretes matter from a large disk (AGN) or from a stellar companion (XRBs, often mediated by a disk). Together with unclassified sources, they account for nearly all of the diffuse Galactic background emission. Furthermore, INTEGRAL has created an all-sky map of the 511 keV distribution helping to identify potential dark matter sites. The distribution of Al-26 follows massive star-forming regions and reflects the rotation of the Galaxy. Gamma-ray bursts (GRBs) are detected in the wide field of view (FOV) at a rate of 1 per month, but INTEGRAL's design also enables it to detect GRBs outside its FOV. Previously rare, XRBs with supergiant companions are an emerging class. This underscores INTEGRAL's ability to peer through the dust that enshrouds these sources and which made them invisible to previous X-ray surveys. Their increasing numbers (as well as those of other classes) offer larger samples on which to perform statistical analyses. A synthetic view of populations of γ-ray sources is instrumental for highlighting signatures of stellar and galactic evolution. In addition, it permits a speculation on the nature of the roughly 100 sources that remain unclassified.

The location of the main emitting region responsible for the bulk of the Blazar emission is a puzzling issue in our understanding of jetted Active Galactic Nuclei. Fast flares and a high Compton dominance are more easily explained if the gamma-ray zone is well inside the Broad Line Region (BLR), while the absence of γ-γ absorption features in the Fermi-LAT spectra as well as the detection at Very High Energies (VHE) of some FSRQ put the blazar zone at much larger distances along the jet, beyond the BLR. The latter seems now to be the most typical behavior in FSRQ, questioning SED models based on the external Compton process on BLR photons.

During the last year the Gamma-Ray sky has glowed of new light: the PAMELA experiment, the Pierre Auger Observatory, the AGILE satellite, and the Fermi Gamma-ray Space Telescope are contributing in an unprecedented way to the unveiling of the cosmic distribution of gamma-ray sources and their viable relation with cosmic rays. The Alpha Magnetic Spectrometer, to be launched next July 2010, will add, for the first time, a precious energetic window, up to a few TeV, to this exciting investigation. We analyze the perspectives of AMS results and the possibilities for the detection of Galactic and Extragalactic gamma-ray astrophysical sources like Pulsars, Microquasars, Gamma-Ray Bursts, and Active Galactic Nuclei.

The radio-loud active galactic nuclei having the radio emission arising from a core region rather than from lobes are often referred to as “blazars” and include Flat Spectrum Radio Quasars (FSRQ) and BL Lacertae (BL Lac) objects. We present results of long term observations of FSRQs as well as BL Lac type objects by SHALON Cherenkov telescopic system at energies > 800 GeV.