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We propose a straightforward and efficient mechanism for the high-energy emission of relativistic astrophysical jets associated with an exchange of interacting high-energy photons between the jet and the external environment. Physical…
Even though the prompt emission of gamma-ray bursts (GRBs) is highly beamed, high-latitude emission still produces a distinct light curve break after the intrinsic emission ceases and the edge of the jet comes into view. This curvature…
The spectacular images of the M87 black hole taken by the Event Horizon Telescope (EHT) have opened a new era of black hole research. One of the next issues is to take polarization images around the central black hole (BH). Since radio…
The high polarization observed in the prompt phase of some gamma-ray bursts (GRBs) arouses extensive studies on the emission mechanism. In this paper, we investigate the polarization properties of the synchrotron-self-Compton (SSC) process…
The magnetic field structure in GRB outflows is of great interest as it can provide valuable clues that can help pin down the mechanism responsible for the acceleration and collimation of GRB jets. The most promising way of probing it is…
Long duration gamma-ray bursts (GRBs), the brightest events since the Big Bang itself, are believed to originate in an ultra-relativistic jet breaking out from a massive stellar envelope. Despite decades of study, there is still no…
High-energy photons propagating in the magnetised medium with large velocity gradients can mediate energy and momentum exchange. Conversion of these photons into electron-positron pairs in the field of soft photons with the consequent…
The dynamics of GRB jets during the afterglow phase is most reliably and accurately modelled using hydrodynamic simulations. All published simulations, however, have considered only a uniform external medium, while a stratified external…
We numerically compute light and polarisation curves of gamma-ray burst afterglows for various configurations of the jet luminosity structure and for different dynamical evolutions. We especially consider the standard homogeneous ``top…
The underlying plasma composition of relativistic extragalactic jets remains largely unknown. Relativistic magnetohydrodynamic (RMHD) models are able to reproduce many of the observed macroscopic features of these outflows. The nonthermal…
We explore the impact of "slow-light" radiative transfer - i.e., general relativistic radiative transfer (GRRT) calculations in which the simulated fluid evolves while light rays are propagating through it - in general relativistic…
Photons that decouple from a relativistic jet do so over a range of radii, which leads to a spreading in arrival times at the observer. Therefore, changes to the comoving photon distribution across the decoupling zone are encoded in the…
High-resolution Very-Long-Baseline Interferometry observations of NGC 1052 show a two sided jet with several regions of enhanced emission and a clear emission gap between the two jets.This gap shrinks with increasing frequency and vanishes…
Growing observational evidence supports the proposition that gamma-ray bursts (GRBs) are powered by relativistic jets from massive helium stars whose cores have collapsed to black holes and an accretion disk (collapsars). We model the…
Radiation-mediated shocks (RMSs) occurring below the photosphere in a gamma-ray burst (GRB) jet could play a crucial role in shaping the prompt emission. In this paper, we study the time-resolved signal expected from such early shocks. We…
The almost simultaneous detection of GRB170817A and GW170817 ushered in nearly a decade of interest in binary neutron star mergers and their multi-messenger signals, resulting in a greater understanding of the processes that produce…
The energy dissipation mechanism within Gamma-Ray Burst (GRB) outflows, driving their extremely luminous prompt $\gamma$-ray emission is still uncertain. The leading candidates are internal shocks and magnetic reconnection. While the…
We examine millisecond magnetars as central engines of Gamma Ray Bursts' (GRB) prompt emission. Using the proto-magnetar wind model of Metzger et al. 2011, we estimate the temporal evolution of the magnetization and power injection at the…
The collimation and evolution of relativistic outflows in $\gamma$-ray bursts (GRBs) are determined by their interaction with the stellar envelope through which they travel before reaching the much larger distance where the energy is…
Despite their discovery about half a century ago, the Gamma-ray burst (GRB) prompt emission mechanism is still not well understood. Theoretical modeling of the prompt emission has advanced considerably due to new computational tools and…