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The unexpected clustering of the optical afterglow luminosities
M. Nardini, G. Ghisellini, G. Ghirlanda +3
We studied the behaviour of the optical afterglow lightcurves of a sample of 24 Gamma--Ray Bursts (GRBs) with known redshift and published estimates of the optical extinction in th…
The jet/disk connection in AGN: Chandra and XMM observations of three powerful radio-loud quasars
R. M. Sambruna, M. Gliozzi, F. Tavecchio +2
The connection between the accretion process that powers AGN and the formation of jets is still poorly understood. Here we tackle this issue using new, deep \chandra and \xmm obser…
Shedding New Light on the 3C 273 Jet with the Spitzer Space Telescope
Y. Uchiyama, C. M. Urry, C. C. Cheung +7
We have performed infrared imaging of the jet of the quasar 3C 273 at wavelengths 3.6 and 5.8 microns with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. When com…
Are GRB 980425 and GRB 031203 real outliers or twins of GRB 060218?
G. Ghisellini, G. Ghirlanda, S. Mereghetti +3
GRB 980425 and GRB 031203 are apparently two outliers with respect to the correlation between the isotropic equivalent energy E_iso emitted in the prompt radiation phase and the pe…
XMM-Newton observations of a sample of gamma-ray loud active galactic nuclei
L. Foschini, G. Ghisellini, C. M. Raiteri +7
(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…
Simultaneous X-ray and optical observations of S5 0716+714 after the outburst of March 2004
L. Foschini, G. Tagliaferri, E. Pian +6
At the end of March 2004, the blazar S5 0716+714 underwent an optical outburst that prompted for quasi-simultaneous target-of-opportunity observations with the INTEGRAL and XMM-New…
Discovery of an Extreme MeV Blazar with the Swift Burst Alert Telescope
Rita M. Sambruna
The Burst Alert Telescope (BAT) onboard Swift detected bright emission from 15--195 keV from the source SWIFT~J0746.3+2548 (J0746 in the following), identified with the optically-f…
Long-Term X-Ray and TeV variability of Mrk 501
M. Gliozzi, R. Sambruna, I. Jung +3
We present X-ray observations of the blazar Mrk501 obtained with RXTE during 1997, 1998, 1999, 2000, and 2004. The goal of this study is twofold: 1) characterize the long-term X-ra…
Hard TeV spectra of blazars and the constraints to the IR intergalactic background
K. Katarzynski, G. Ghisellini, F. Tavecchio +2
Recent gamma-ray observations of the blazar 1ES 1101-232 (redshift z=0.186) reveal that the unabsorbed TeV spectrum is hard, with spectral index [$F(ν) \propto ν^{-…
Jet deceleration: the case of PKS 1136-135
F. Tavecchio, L. Maraschi, R. M. Sambruna
Modeling the multiwavelength emission of successive regions in the jet of the quasar PKS 1136-135 we find indication that the jet suffers deceleration near its end. Adopting a cont…
A Short Hard X-ray Flare from the Blazar NRAO 530 Observed by INTEGRAL
L. Foschini, E. Pian, L. Maraschi +6
We report about a short flare from the blazar NRAO 530 occurred on 17 February 2004 and detected serendipitously by the IBIS/ISGRI detector on board INTEGRAL. In the 20-40 keV ener…