A5001538936- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Astro and Planetary Science
- Black Holes and Theoretical Physics
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Relativity and Gravitational Theory
- Neutrino Physics Research
- Dark Matter and Cosmic Phenomena
- Geophysics and Gravity Measurements
- Galaxies: Formation, Evolution, Phenomena
- Solar and Space Plasma Dynamics
- Noncommutative and Quantum Gravity Theories
- Astronomical Observations and Instrumentation
- Astrophysics and Star Formation Studies
- High-pressure geophysics and materials
- Laser-Plasma Interactions and Diagnostics
- Radio Astronomy Observations and Technology
- Particle physics theoretical and experimental studies
- Quantum Electrodynamics and Casimir Effect
- Quantum Mechanics and Applications
- Statistical and numerical algorithms
Hebrew University of Jerusalem
2015-2024
Hebrew College
1999-2024
Centre National de la Recherche Scientifique
2017-2022
Sorbonne Université
2022
Institut National de Physique Nucléaire et de Physique des Particules
2022
Laboratoire de Physique Nucléaire et de Hautes Énergies
2022
Czech Academy of Sciences, Institute of Physics
1975-2019
OHB (Italy)
2018
Laboratoire AstroParticule et Cosmologie
2017
Université Paris Cité
2017
Gamma-ray bursts (GRB's), short and intense pulses of low-energy $\ensuremath{\gamma}$ rays, have fascinated astronomers astrophysicists since their unexpected discovery in the late sixties. During last decade, several space missions---BATSE (Burst Transient Source Experiment) on Compton Gamma-Ray Observatory, BeppoSAX now HETE II (High-Energy Explorer)---together with ground-based optical, infrared, radio observatories revolutionized our understanding GRB's, showing that they are...
The recently discovered gamma-ray burst afterglow is believed to be described reasonably well by synchrotron emission from a decelerating relativistic shell that collides with an external medium. To compare theoretical models observations, we calculate here the broadband spectrum and corresponding light curve of radiation power-law distribution electrons in expanding shock. Both consist several segments related indices. constructed under two limiting for hydrodynamic evolution shock: fully...
Gamma-ray bursts (GRBs) have puzzled astronomers since their accidental discovery in the late 1960s. The BATSE detector on COMPTON-GRO satellite has been detecting one burst per day for last six years. Its findings revolutionized our ideas about nature of these objects. They shown that GRBs are at cosmological distances. This idea was accepted with difficulties first. recent an X-ray afterglow by Italian/Dutch BeppoSAX led to a detection high red-shift absorption lines optical GRB970508 and...
In the afterglows of several gamma-ray bursts (GRBs), rapid temporal decay, which is inconsistent with spherical (isotropic) blast-wave models, observed. particular, GRB 980519 had most rapidly fading well-documented afterglows, t-2.05±0.04 in optical as well X-rays. We show that such decay more consistent evolution a jet after it slows down and spreads laterally, for t-p expected (where p index electron energy distribution). Such beaming model would relax requirements on some extreme GRBs...
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We discuss the possibility that gamma-ray bursts result from internal shocks in an ultra-relativistic matter. Using a simple model we calculate temporal structure and estimate efficiency of this process. In matter flow is represented by succession shells with random values Lorentz factor. take place between those resulting emission. Internal can produce highly variable observed most provided source emitting relativistic variable. The peaks are almost one to correlation activity source. A...
Gravitational waves have been detected from a binary neutron star merger event, GW170817. The detection of electromagnetic radiation the same source has shown that occurred in outskirts galaxy NGC 4993, at distance 40 megaparsecs Earth. We report counterpart radio appears 16 days after allowing us to diagnose energetics and environment merger. observed emission can be explained by either collimated ultra-relativistic jet viewed off-axis, or cocoon mildly relativistic ejecta. Within 100...
According to the internal-external shocks model for gamma-ray bursts (GRBs), GRB is produced by internal within a relativistic flow while afterglow external with interstellar medium. We explore early emission. For short GRBs peak of will be delayed, typically few dozens seconds after burst. long emission overlap signal. calculate expected spectrum and light curves in optical, X-ray, bands. These characteristics provide way discriminate between late (part GRB) If such delayed emission,...
Merging neutron stars offer an exquisite laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of electromagnetic counterpart EM170817 to gravitational waves (GW170817) detected from merging stars. By synthesizing a panchromatic dataset, we demonstrate that are long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma-rays seen dissimilar classical short gamma-ray bursts with...
We invert directly the redshift–luminosity distribution of observed long Swift gamma-ray bursts (GRBs) to obtain their rate and luminosity function. Our best-fitting is described by a broken power law that rises like for 0 < z 3 decreases > 3. The local ρ0≃ 1.3+0.6−0.7 (Gpc−3 yr−1). function well with break at L*≃ 1052.5±0.2 (erg s−1) indices α= 0.2+0.2−0.1 β= 1.4+0.3−0.6. recently detected GRB 090423, z≈ 8, fits nicely into model's prediction, verifying we are allowed extend our results...
A tidal disruption event (TDE) takes place when a star passes near enough to massive black hole be disrupted. About half the star's matter is given elliptical trajectories with large apocenter distances, and other unbound. To form an accretion flow, bound must lose significant amount of energy, actual depending on characteristic scale flow measured in units hole's gravitational radius ( erg). Recent numerical simulations have revealed that close most initial orbits, cm from hole,...
We estimate the rate and luminosity function of short (hard) Gamma-Ray Bursts (sGRBs) that are non-Collapsars, using peak fluxes redshifts BATSE, Swift Fermi GRBs. Following Bromberg2013 we select a sub-sample bursts which most likely non-Collapsars. find these sGRBs delayed relative to global star formation (SFR) with typical delay time 3-4 Gyr (depending on SFR model). However, if two or three sGRB at high have been missed because selection effects, distribution times ~1/t would be also...
Abstract Long-duration (>2 s) γ-ray bursts that are believed to originate from the death of massive stars expected be accompanied by supernovae. GRB 060614, lasted 102 s, lacks a supernova-like emission down very stringent limits and its physical origin is still debated. Here we report discovery near-infrared bump significantly above regular decaying afterglow. This red inconsistent with even weakest known supernova. However, it can arise Li-Paczyński macronova—the radioactive decay...
Compact binary mergers are prime sources of gravitational waves (GWs), targeted by current and next generation detectors. The question 'what is the observable electromagnetic (EM) signature a compact merger?' an intriguing one with crucial consequences to quest for GWs. We present large set numerical simulations that focus on EM signals emerge from dynamically ejected subrelativistic material. These outflows produce time-scale day macronovae – short-lived infrared (IR) ultraviolet (UV)...
We follow the longterm evolution of dynamic ejecta neutron star mergers for up to 100 years and over a density range roughly 40 orders magnitude. include nuclear energy input from freshly synthesized, radioactively decaying nuclei in our simulations study its effects on remnant dynamics. Although heating substantially alters evolution, we find that running networks purely hydrodynamic (i.e. without heating) yields actually acceptable nucleosynthesis results. The main effect radioactive is...
We use 3D hydrodynamic simulations of the long-term evolution neutron star merger ejecta to predict light curves electromagnetic transients that are powered by decay freshly produced r-process nuclei. For dynamic launched tidal and interaction, we adopt grey opacities 10 cm$^2$/g, as suggested recent studies. our reference case a 1.3-1.4 $M_\odot$ merger, find broad IR peak 2-4 d after merger. The luminosity is $\approx 2\times 10^{40}$ erg/s for an average orientation, but increased up...