Related papers: Infrared to X-ray observations of PKS 2155-304 in …

We have used all 20 archival XMM-Newton observations of PKS 2155-304 with simultaneous X-ray and UV/optical data to study its long term flux and spectral variability. We find significant variations, in all bands, on time-scales of years…

The aim of this paper is to study the evolution of the broadband spectrum of one of the brightest and nearest quasars 3C 273. We analyze the data obtained during quasi-simultaneous INTEGRAL and XMM monitoring of the blazar 3C 273 in…

In this paper we analyse five observations of the BL Lac object AO 0235+16 performed with the Chandra and XMM-Newton satellites during the years 2000-2005. In the February 2002 observation the source is found in a bright state and presents…

Gamma-ray emitting blazars have been the targets of many recent or ongoing monitoring programmes. The resulting multi-wavelength data archives are ideal for studying the quiescent and variable behaviour of the blazar PKS 2155-304. Here,…

The high frequency peaked blazar PKS 2155-304 is one of the brightest and most intensively studied prototype of BL Lac objects. Gamma-rays from PKS 2155-304 have been detected from the MeV to TeV ranges. We computed a synchrotron…

This paper presents a detailed analysis of the temporal and spectral variability of the low-energy peaked BL Lac object S5 0716+714 with a long (~74 ks)X-ray observation performed by XMM-Newton on 2007 September 24-25. The source…

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…

Observations of very high energy gamma-rays from blazars provide information about acceleration mechanisms occurring in their innermost regions. Studies of variability in these objects allow a better understanding of the mechanisms at play.…

We report on multiwavelength observations of the blazar PKS 0537-441 (z = 0.896) obtained from microwaves through gamma rays by SMA, REM, ATOM, Swift and Fermi during 2008 August-2010 April. Strong variability has been observed in gamma…

We present the analysis and the results of a 20 ks XMM-Newton observation of the extremely X-ray loud (L_X ~ 5 x 10^{47} erg/s) flat-spectrum radio quasar RBS 315 at a redshift of 2.69. This EPIC observation has allowed us to strongly…

We present the results of the power spectral density (PSD) analysis for the blazars Mrk\,421 and PKS\,2155$-$304, using good-quality, densely sampled light curves at multiple frequencies, covering 17 decades of the electromagnetic spectrum,…

With currently available XMM-Newton EPIC pn observations spanned over about 3 years, we present a detailed spectral and temporal variability of the 0.2--10 keV X-ray emission from the X-ray bright BL Lac object PKS 2155-304. The spectral…

The optical-UV and X-ray instruments on-board XMM-Ndewton provide an excellent opportunity to perform simultaneous observations of violently variable objects over a broad wavelength range. The UV and X-ray bright BL Lac object PKS 2155-304…

The origin and physics of X-ray intra-day variability (IDV) in blazars, which is a long-standing issue, is studied by modelling the broad-band X-ray spectrum, the light curves (LCs), and the Fourier time lags. We present the timing analysis…

In 2007-2008 we carried out a new multiwavelength campaign of the Whole Earth Blazar Telescope (WEBT) on BL Lacertae, involving three pointings by the XMM-Newton satellite, to study its emission properties. The source was monitored in the…

The addition of a 28 m Cherenkov telescope (CT5) to the H.E.S.S. array extended the experiment's sensitivity to lower energies, providing new opportunities for studies of Active Galactic Nuclei (AGNs) with soft intrinsic spectra and at high…

We present a comprehensive study of the X-ray spectral variability observed in 13 TeV photon emitting high energy peaked BL Lacs(HBLs). These data come from 54 XMM-Newton EPIC-PN pointed observations made during its operational period from…

We present a comprehensive 20-year multiwavelength variability study of the blazar PKS 2155-304, one of the most luminous and extensively monitored high-frequency-peaked BL Lac objects in the southern hemisphere. Using Fermi-LAT…

PKS 2155-304 is one of the prototypes of BL Lac objects. Its spectral energy distribution is known from the radio to the TeV band and has two peaks, one in the soft X-rays and the other in the TeV region. These may be interpreted within the…

Aim of this work is a broad-band study with INTEGRAL, Swift and XMM-Newton satellites of a sample of 9 blazars (7 FSRQ and 2 BL Lac) with redshift up to about 4. The spectral analysis has shown clear evidence of a flattening of the…