A5009071661- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Radio Astronomy Observations and Technology
- Pulsars and Gravitational Waves Research
- Neutrino Physics Research
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Solar and Space Plasma Dynamics
- Particle Accelerators and Free-Electron Lasers
- Astronomical Observations and Instrumentation
- High-pressure geophysics and materials
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Methane Hydrates and Related Phenomena
- Corneal surgery and disorders
- Cosmology and Gravitation Theories
- Geomagnetism and Paleomagnetism Studies
- Gyrotron and Vacuum Electronics Research
- Nonlinear Waves and Solitons
- Glaucoma and retinal disorders
- Astrophysics and Star Formation Studies
- Ocular and Laser Science Research
- Particle accelerators and beam dynamics
- SAS software applications and methods
Universitat de València
2010-2019
Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
2016
Sapienza University of Rome
2015
Max Planck Institute for Astrophysics
2003-2006
Max Planck Society
2003-2005
Mineral Products Association
2005
Tidal disruption events (TDEs) are transient flares produced when a star is ripped apart by the gravitational field of supermassive black hole (SMBH). We have observed source in western nucleus merging galaxy pair Arp 299 that radiated >1.5x10^52 erg infrared and radio, but was not luminous at optical or X-ray wavelengths. interpret this as TDE with much its emission re-radiated wavelengths dust. Efficient reprocessing dense gas dust may explain difference between theoretical predictions...
We present numerical simulations of the spectral evolution and emission radio components in relativistic jets. compute jet models by means a hydrodynamics code. have developed an algorithm (SPEV) for transport population nonthermal electrons including radiative losses. For large values ratio gas pressure to magnetic field energy density, αB ∼ 6 × 104, quiescent show substantial evolution, with observational consequences only above frequencies. Larger (αB 102), such that synchrotron losses...
The temporal and spatial spectral evolution of the jets AGN can be studied with multi-frequency, multi-epoch VLBI observations. combination both, morphological parameters used to derive source intrinsic physical properties such as magnetic field non-thermal particle density. In first two papers this series, we analyzed single-dish light curves kinematics blazar CTA 102 suggested a shock-shock interaction between traveling standing shock wave possible scenario explain observed component...
The recent transient event Swift J1644+57 has been interpreted as emission from a collimated relativistic jet, powered by the sudden onset of accretion onto supermassive black hole following tidal disruption star. Here we model radio-microwave synchrotron radiation produced shock interaction between jet and gaseous circumnuclear medium (CNM). At early times after (t < 5-10 days) reverse propagates through decelerates ejecta, while at later outflow approaches Blandford-McKee self-similar...
<i>Context. <i/>The role of magnetic fields in gamma-ray burst (GRB) flows remains debated. If sufficient strength, they can leave their signature on the initial phases afterglow by substantially changing backreaction flow as a consequence its interaction with external medium.<i>Aims. <i/>We attempt to understand quantitatively dynamical effect and observational signatures GRB ejecta magnetization onset afterglow.<i>Methods. perform ultrahigh-resolution, one-dimensional, relativistic MHD...
We model the non-thermal transient Swift J1644+57 as resulting from a relativistic jet powered by accretion of tidally-disrupted star onto super-massive black hole. Accompanying synchrotron radio emission is produced shock interaction between and dense circumnuclear medium, similar to gamma-ray burst afterglow. An open mystery, however, origin late-time rebrightening, which occurred well after peak jetted X-ray emission. Here, we systematically explore several proposed explanations for this...
High resolution Very Long Baseline Interferometry (VLBI) observations of Active Galactic Nuclei (AGN) revealed traveling and stationary or quasi-stationary radio-components in several blazar jets. The ones are general interpreted as shock waves generated by pressure perturbations injected at the jet nozzle. features can be recollimation shocks non-pressure matched jets if they show a quasi-symmetric bump spectral index distribution. In some there may interactions between two kinds shocks....
Dozens of stellar tidal disruption events (TDEs) have been identified at optical, UV and X-ray wavelengths. A small fraction these, most notably Swift J1644+57, produce radio synchrotron emission, consistent with a powerful, relativistic jet shocking the surrounding circumnuclear gas. The dearth similar non-thermal emission in majority TDEs may imply that powerful formation is intrinsically rare, or conditions galactic nuclei are typically unfavourable for producing detectable signal. Here...
Aims. We investigate the role played by a pre-supernova (SN) ambient magnetic field on dynamics of expanding remnant SN 1987A and origin evolution radio emission from remnant, in particular, during interaction blast wave with nebula surrounding SN. Methods. model breakout shock at stellar surface to expansion its through 3D MHD simulations. The considers radiative cooling, deviations equilibrium ionization, deviation temperature-equilibration between electrons ions, plausible configuration...
We obtain renormalized sets of right and left eigenvectors the flux vector Jacobians relativistic MHD equations, which are regular span a complete basis in any physical state including degenerate ones. The renormalization procedure relies on characterization degeneracy types terms normal tangential components magnetic field to wavefront fluid rest frame. Proper expressions conserved variables obtained through corresponding matrix transformations. Our work completes previous analysis that...
Context. Very Long Baseline Interferometry (VLBI) observations can resolve the radio structure of active galactic nuclei (AGN) and provide estimates structural kinematic characteristics on parsec-scales in their jets. The changes kinematics observed jet features be used to study physical conditions innermost regions these sources. We performed multifrequency multiepoch Array (VLBA) blazar CTA 102 during its 2006 flare, strongest ever reported for this source. These an excellent opportunity...
The role of magnetic fields in gamma-ray burst (GRB) flows remains controversial. study the early afterglow phases and, particular, reverse shock dynamics and associated emission offers a promising probe magnetization ejecta. In this paper, we derive conditions for existence arbitrarily magnetized ejecta that decelerate interact with circumburst medium. Both constant wind-like density profiles are considered. We show, contrast to previous estimates, 1 not crossed by large fraction parameter...
Aims. We study the collision of magnetized irregularities (shells) in relativistic outflows order to explain origin generic phenomenology observed non-thermal emission both blazars and gamma-ray bursts. focus on influence magnetic field dynamics, we investigate how properties radiation depend strength initial internal energy density flow.
We study the dynamic efficiency of conversion kinetic-to-thermal/magnetic energy internal shocks in relativistic magnetized outflows. model as being caused by collisions shells plasma with same flux and a non-zero relative velocity. The contact surface, where interaction between takes place, can break up either into two oppositely moving (in frame surface is at rest), or reverse shock forward rarefaction. find that for moderately (magnetization σ≃ 0.1), single two-shell be large 40 per cent....
Common models of blazars and gamma-ray bursts assume that the plasma underlying observed phenomenology is magnetized to some extent. Within this context, radiative signatures dissipation kinetic conversion magnetic energy in internal shocks relativistic outflows are studied. We model as being caused by collisions homogeneous shells. compute flow state after shell interaction solving Riemann problems at contact surface between colliding shells, then emission from resulting shocks. Under...
We present the results of a detailed temporal analysis bright BL Lac object Mrk 421 using three available long timing mode observations by EPIC PN camera. This detector is characterized its life time and largely free photon pile-up problems. The source was found in different intensity variability states differing up to more than factor count rate. A resolved cross correlation between soft hard energy bands revealed that characteristics correlated emission, with lags both signs, change on...
We use high-resolution relativistic magnetohydrodynamics simulations coupled with a radiative transfer code to compute multiwavelength afterglow light curves of magnetized ejecta gamma-ray bursts interacting uniform circumburst medium. The aim our study is determine how the magnetization at large distance from central engine influences emission, and assess whether observations can be reliably used infer strength magnetic field. find that, for typical parameters ejecta, emission reverse shock...
We present the results of relativistic hydrodynamic simulations collision two dense shells in a uniform external medium, as envisaged internal shock model for BL Lac jets. The non-thermal radiation produced by highly energetic electrons injected at shocks is computed following their temporal and spatial evolution. acceleration parametrized using different models corresponding X-ray light curves are computed. find that interaction time scale influenced an with medium. For chosen parameter...
The afterglow emission that follows gamma-ray bursts (GRBs) contains valuable information about the circumburst medium and, therefore, GRB progenitor. Theoretical studies of blast waves, however, are often limited to simple density profiles for external (mostly constant and power-law R^{-k} ones). We argue a large fraction long-duration GRBs should take place in massive stellar clusters where is much more complicated. As case study, we simulate propagation wave shaped by collision winds O...
Blackbody-dominated (BBD) gamma-ray bursts (GRBs) are events characterized by long durations and the presence of a significant thermal component following prompt emission, as well absence typical afterglow. GRB 101225A is most prominent member this class. A plausible progenitor system for it BBD-GRBs merger neutron star helium core an evolved, massive star. Using relativistic hydrodynamic simulations we model propagation ultrarelativistic jets through environments created such mergers. In...
We present results of a detailed numerical study and theoretical analysis the dynamics internal shocks in relativistic jets non-thermal flares associated with these shocks. In our model result from collisions density inhomogeneities (shells) jet flows. find that merged shell resulting inelastic collision shells has complicated structure due to non-linear interaction. Furthermore, instantaneous efficiency for converting kinetic energy into thermal is found be almost twice as high...
GRB 101225A is a prototype of the class blackbody-dominated (BBD) gamma-ray bursts (GRBs). It has been suggested that BBD-GRBs result from merger binary system formed by neutron star and helium core an evolved star. We have modelled propagation ultrarelativistic jets through environment left behind means relativistic hydrodynamic simulations. In this paper, output our numerical models post-processed to obtain (thermal) radiative signature resulting outflow. outline most relevant dynamical...