Related papers: Coordinated RXTE and multiwavelength observations …
Results obtained with BeppoSAX observations of blazars within various collaborative programs are presented. The spectral similarity "paradigm", whereby the spectral energy distributions of blazars follow a sequence, leading to a unified…
X-ray polarization is a unique new probe of the particle acceleration in astrophysical jets made possible through the Imaging X-ray Polarimetry Explorer. Here we report on the first dense X-ray polarization monitoring campaign on the blazar…
With their jet pointing towards us, blazars are ideal tools to study the physics and structure of extragalactic jets. Their powerful jets are cosmic particle accelerators and are alleged to be one of the production sites of the high-energy…
The author is developing a numerical code with thousands of emission zones to simulate the time-dependent multi-waveband emission from blazars. The code is based on a model in which turbulent plasma flowing at a relativistic speed down a…
The observational evidence for jets and phenomena arising from rotation powered radio pulsars is reviewed, including many recent and exciting discoveries at X-ray wavelengths. The well studied jets of the Crab pulsar are summarised,…
During the first 3 years of operation the Gamma-Ray Imaging Detector onboard the AGILE satellite detected several blazars in a high gamma-ray activity: 3C 279, 3C 454.3, PKS 1510-089, S5 0716+714, 3C 273, W Comae, Mrk 421, PKS 0537-441 and…
The current status of leptonic jet models for blazars is reviewed. Differences between the quasar and BL-Lac subclasses of blazars may be understood in terms of the dominance of different radiation mechanisms in the gamma-ray regime.…
The origin of the high-energy emission in astrophysical jets from black holes is a highly debated issue. This is particularly true for jets from supermassive black holes that are among the most powerful particle accelerators in the…
Aims. The blazars Mrk 421 and Mrk 501 have shown multiwavelength variability on all observed timescales, and have been well studied at high energies on short timescales. We aim to characterise the long-term temporal behaviour of these…
In the present paper, we have reported the result of simultaneous multi-wavelength observations of the TeV blazar Mrk 421 during February $-$ March 2003. In this period, we have observed Mrk 421 using Pachmarhi Array of \v{C}erenkov…
The polarization of X-ray synchrotron emission in blazars directly probes the magnetic field geometry and particle acceleration processes in relativistic jets. We use particle-in-cell simulations of magnetic reconnection and magnetized…
We are performing an unprecedentedly long and dense monitoring of the multi-frequency (radio to TeV) emission from the classical TeV blazars Mkn 421 and Mkn 501. These objects are among the brightest X-ray/TeV blazars in the sky and among…
We report results from a systematic search for X-ray flares from Mrk 421, using archival data from the Rossi X-ray Timing Explorer (RXTE) satellite. The flares are clearly seen over a wide range of timescales. The quasi-continuous coverage…
Active Galactic Nuclei (AGN) are known to show significant variability over a wide frequency range. We review observational results on the variability characteristics of blazars in the very high energy (VHE) domain, focusing on recent…
We conducted a daily monitoring campaign on Mrk 421 in 2003 and 2004 with the Whipple 10 m telescope and the large-area instruments aboard RXTE, simultaneously covering TeV and X-ray energies. Supporting observations at optical and radio…
We report simultaneous multi-frequency observations of the blazar PG 1553+113, that were carried out in March-April 2008. Optical, X-ray, high-energy (HE; greater than 100 MeV) gamma-ray, and very-high- energy (VHE; greater than 100 GeV)…
There have been a number of recent spectral models that have been successful in reproducing the observed X-ray spectra of galactic black hole candidates (GBHC). However, there still exists controversy over such issues as: what are the…
Although the gamma-ray emission in blazars dominates the power output, there are crucial informations carried by the X-rays. Indeed, their paucity, together with the short variability timescales observed both at X and gamma-ray energies…
We present timing analysis for a Rossi X-ray Timing Explorer observation of Cygnus X-1 in its hard/low state. This was the first RXTE observation of Cyg X-1 taken after it transited back to this state from its soft/high state. RXTE's large…
We present the results of the optical monitoring of 18 southern blazars in the V and R Johnson-Cousins bands. Our main objective is to study the variations in the optical flux and theis relationship with the colour and spectral…