Related papers: Probing the Transition Between the Synchrotron and…
PKS 1510-089 is one of the most variable blazars. Very high energy gamma ray emission from this source was observed by H.E.S.S. during March-April 2009 and by MAGIC from February 3 to April 3, 2012 quasi-simultaneously with multi-wavelength…
Extreme high-energy peaked BL Lac objects (EHBLs) are an emerging class of blazars with exceptional spectral properties. The non-thermal emission of the relativistic jet peaks in the spectral energy distribution (SED) plot with the…
The black hole binary GS 2023+338 exhibited an unprecedently bright outburst on June 2015. Since June 17th, the high energy instruments on board INTEGRAL detected an extremely variable emission during both bright and low luminosity phases,…
Observations of binary systems obtained recently with the High Energy Stereoscopic System (H.E.S.S) of Cherenkov telescopes are reported. The outcomes of a detailed observation campaign on PSR B1259-63 during its periastron passage in 2014…
We summarize the results of BeppoSAX ToO observation of blazars that were known to be in a high state from observations carried out in the optical or X-ray or TeV bands.In some of the observed sources, two spectral components were detected,…
The extragalactic VHE gamma-ray sky is rich in blazars. These are jetted active galactic nuclei viewed at a small angle to the line-of-sight. Only a handful of objects viewed at a larger angle are known so far to emit above 100 GeV.…
We present the results of a multi-wavelength study of a population of X-ray bright ($\rm log(F_{0.2-12 \ keV})>-12.5$), non-$\gamma$-ray detected high and extreme high synchrotron peak (HSP, EHSP; $\rm log(\nu_{\rm peak,\ Hz})>16$) BL Lacs…
AIMS: Our goal is to understand the nature of blazars and the mechanisms for the generation of high-energy gamma-rays, through the investigation of the prototypical blazar PKS 2155-304, which shows complex behaviour. METHODS: We analyze…
This paper reports X-ray spectral observations of a relatively nearby z = 0.048 BL Lacertae (BL Lac) object 1ES1959+650, which is a potential TeV emitter. The observations include 31 short pointings made by the Unconventional Stellar Aspect…
Blazars are classified into high, intermediate and low energy peaked sources based on the location of their synchrotron peak. This lies in infra-red/optical to ultra-violet bands for low and intermediate peaked blazars. The transition from…
The BL Lacertae (BL Lac) object 1ES 2344+514 (1ES 2344), at a redshift of 0.044, was discovered as a source of very high energy (VHE) gamma rays by the Whipple Collaboration in 1995 \citep{2344Catanese98}. This detection was recently…
The non-thermal spectra of blazars, observed from radio to GeV/TeV gamma-rays, reveal two pronounced components, both produced by radiation by energetic particles. One peaks in the IR - to soft X-ray band, radiating via the synchrotron…
PKS 0537-441, a bright gamma-ray emitting blazar, was observed at radio, optical, UV and X-ray frequencies during various EGRET pointings, often quasi-simultaneously. In 1995 the object was found in an intense emission state at all…
Mrk501 is a very high-energy (VHE) gamma-ray blazar located at z=0.034. During a period of two weeks in July 2014, the highest X-ray activity of Mrk501 was observed in ~14 years of operation of the Neil Gehrels Swift Gamma-ray Burst…
The very-high-energy (VHE, $\gtrsim 100$ GeV) $\gamma$-ray MAGIC observations of the blazar S4 0954+65, were triggered by an exceptionally high flux state of emission in the optical. This blazar has a disputed redshift of z=0.368 or…
(abridged) We performed a homogeneous and systematic analysis of simultaneous X-ray and optical/UV properties of a group of 15 gamma-ray loud AGN, using observations performed with XMM-Newton. The sample is composed of 13 blazars (6 BL Lac…
Extreme high synchrotron peaked blazars (EHBLs) are amongst the most powerful accelerators found in nature. Usually the synchrotron peak frequency of an EHBL is above $10^{17}\,$Hz, i.e., lies in the range of medium to hard X-rays making…
We study the synchrotron component of the spectral energy distribution (SED) on the sample of 877 blazars using the ASDC SED Builder Tool with available broadband data from the literature. Our sample includes 423 flat-spectrum radio sources…
Extreme high-energy peaked BL Lac objects (EHBLs) are an emerging class of blazars. Their typical two-hump structured spectral energy distribution (SED) peaks at higher energies with respect to conventional blazars. Multi-wavelength (MWL)…
A multiwavelength campaign was organized to take place between March and July of 2012. Excellent temporal coverage was obtained with more than 25 instruments, including the MAGIC, FACT and VERITAS Cherenkov telescopes, the instruments on…