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Despite being hard to measure, GRB prompt $\gamma$-ray emission polarization is a valuable probe of the dominant emission mechanism and the outflow's composition and angular structure. During the prompt emission the outflow is…

High Energy Astrophysical Phenomena · Physics 2020-01-08 Ramandeep Gill , Jonathan Granot , Pawan Kumar

We present the first general relativistic hydrodynamic models of the launch and evolution of relativistic jets and winds, driven by thermal energy deposition, possibly due to neutrino-antineutrino annihilation, in the close vicinity of…

Astrophysics · Physics 2015-06-24 M. A. Aloy , H. -T. Janka , E. Mueller

The observed variability of BL Lac objects and Quasars on timescales <1 day (intraday variability, IDV) have revealed radio brightness temperatures up to 10^{16}-10^{20} K. These values challenge the beaming model with isotropic comoving…

Astrophysics · Physics 2007-05-23 A. R. Crusius-W"atzel , H. Lesch

The beaming pattern of radiation emitted by a relativistically moving source like jets in microquasars, AGN and GRBs, is a key issue for understanding of acceleration and radiation processes in these objects. In this paper we introduce a…

High Energy Astrophysical Phenomena · Physics 2018-05-30 S. R. Kelner , E. Lefa , F. M. Rieger , F. A. Aharonian

Relativistic jets are one of the most powerful manifestations of the release of energy produced around supermassive black holes at the centre of active galactic nuclei (AGN). Their emission is observed across the entire electromagnetic…

High Energy Astrophysical Phenomena · Physics 2015-06-17 M. Orienti , F. D'Ammando , M. Giroletti , D. Dallacasa , T. Venturi , G. Giovannini

Relativistic electrons accelerated by both the first-order and the second-order Fermi accelerations in some synchrotron sources have a hybrid shape of thermal and nonthermal energy distribution. This particle acceleration result is…

High Energy Astrophysical Phenomena · Physics 2018-03-14 Jirong Mao , Jiancheng Wang

We report on the development of a numerical code to calculate the angle-dependent synchrotron + synchrotron self-Compton radiation from relativistic jet sources with partially ordered magnetic fields and anisotropic particle distributions.…

High Energy Astrophysical Phenomena · Physics 2015-06-11 Omar Jamil , Markus Boettcher

In the first of a series of papers investigating emission from blazar jets from radio to high-energy {\gamma}-rays, we revisit the class of models where the jet has a uniform conical ballistic structure. We argue that by using simple…

High Energy Astrophysical Phenomena · Physics 2012-12-13 William J. Potter , Garret Cotter

(Abridged) We analyze blazar jet apparent speeds and accelerations from the RDV series of astrometric and geodetic VLBI experiments. From these experiments, we have produced and analyzed 2753 global VLBI images of 68 sources at 8 GHz with a…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-20 B. G. Piner , A. B. Pushkarev , Y. Y. Kovalev , C. J. Marvin , J. G. Arenson , P. Charlot , A. L. Fey , A. Collioud , P. A. Voitsik

A point-like source of ~TeV gamma-rays has recently been seen towards the Galactic center by HESS and other air Cerenkov telescopes. In recent work (Ballantyne et al. 2007), we demonstrated that these gamma-rays can be attributed to…

Astrophysics · Physics 2009-11-13 Roland M. Crocker , David Jones , David R. Ballantyne , Fulvio Melia

Eleven bright gamma-ray bursts (GRBs) detected by BATSE have also been seen at much higher energies by EGRET, six at energies above 10 MeV. Such observations imply that these bursts are optically thin to photon-photon pair production at all…

Astrophysics · Physics 2009-10-30 Matthew G. Baring , Alice K. Harding

A widely discussed explanation for the origin of the X-ray emission observed from knots in extended quasar jets with the Chandra X-ray Obseratory is Compton-scattered CMBR by electrons with Lorentz factors $\gamma^\prime \sim 10^2$. This…

Astrophysics · Physics 2009-11-10 A. Atoyan , C. D. Dermer

A relativistic electron-positron ($e^{+}e^{-}$) pair wind from a rapidly rotating, strongly magnetized neutron star (NS) would interact with a gamma-ray burst (GRB) external shock and reshapes afterglow emission signatures. Assuming that…

High Energy Astrophysical Phenomena · Physics 2021-09-29 Long Li , Zi-Gao Dai

We have calculated variability Doppler boosting factors, Lorentz factors, and viewing angles for a large sample of sources by using total flux density observations at 22 and 37 GHz and VLBI data. We decomposed the flux curves into…

Astrophysics · Physics 2009-11-13 T. Hovatta , E. Valtaoja , M. Tornikoski , A. Lähteenmäki

The polarimetric measurement on the prompt phase of GRB 100826A shows that the polarization angle changes $\sim 90^{\circ}$ between two adjacent time intervals. We will show that this phenomenon can be naturally interpreted in the framework…

High Energy Astrophysical Phenomena · Physics 2014-11-07 Zhe Chang , Hai-Nan Lin

The detection of the delayed emission in X-ray, optical and radio band, i.e. the afterglow of $\gamma$-ray bursts (GRBs), suggestes that the sources of GRBs are likely to be at cosmological distances. Here we explore the interaction of a…

Astrophysics · Physics 2009-10-30 D. M. Wei , T. Lu

Clues to the physical conditions in radio cores of blazars come from measurements of brightness temperatures as well as effects produced by intrinsic opacity. We study the properties of the ultra compact blazar AO 0235+164 with RadioAstron…

The synchrotron reflection scenario recently proposed to explain $\gamma$-ray flares observed from blazar jets is studied. Our analysis takes into account the angular distribution of the beamed radiation, the finite extent of the scattering…

Astrophysics · Physics 2016-11-23 M. Boettcher , C. D. Dermer

We obtain a system of exact solutions of the Dirac equation for an electron moving in a constant homogeneous external magnetic field with account of its vacuum magnetic moment and assumed Lorentz invariance violation in the minimal CPT-odd…

High Energy Physics - Theory · Physics 2008-11-26 I. E. Frolov , V. Ch. Zhukovsky

Special relativity calculates, by means of the Lorentz gamma factor, the proper time of all inertial systems from the observer proper time, which is taken as a time standard. So, any temporal inference relies in first instance on the…

General Physics · Physics 2010-01-19 G. Sardin