Jonathan Granot
A5005781275- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Dark Matter and Cosmic Phenomena
- Solar and Space Plasma Dynamics
- Particle Detector Development and Performance
- Astronomy and Astrophysical Research
- Neutrino Physics Research
- Astronomical Observations and Instrumentation
- High-pressure geophysics and materials
- Astrophysics and Star Formation Studies
- Cosmology and Gravitation Theories
- Noncommutative and Quantum Gravity Theories
- Particle physics theoretical and experimental studies
- Radio Astronomy Observations and Technology
- Particle Accelerators and Free-Electron Lasers
- SAS software applications and methods
- Geophysics and Gravity Measurements
- Methane Hydrates and Related Phenomena
- Radiation Therapy and Dosimetry
- Nuclear Physics and Applications
- Galaxies: Formation, Evolution, Phenomena
Open University of Israel
2015-2024
Tel Aviv University
2011-2024
George Washington University
2017-2024
Universidad Nacional Autónoma de México
2007-2024
Laboratoire de Physique des 2 Infinis Irène Joliot-Curie
2023
TU Dortmund University
2023
University of Łódź
2023
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
2023
University of Turku
2023
Niels Brock
2023
We present new observations of the early X-ray afterglows first 27 gamma-ray bursts (GRBs) well observed by Swift X-Ray Telescope (XRT). The show a canonical behavior, where light curve broadly consists three distinct power-law segments: (1) an initial very steep decay (∝t-α with 3 ≲ α1 5), followed (2) shallow (0.5 α2 1.0), and finally (3) somewhat steeper (1 α3 1.5). These segments are separated two corresponding break times, tbreak,1 500 s 103 tbreak,2 104 s. On top this many events have...
Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Burst Monitor and Large Area Telescope onboard Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades gammaray energy. In September 2008, observed exceptionally luminous GRB 080916C, with largest apparent release yet measured. high-energy gamma rays to start later persist longer than lower photons. A simple spectral form fits entire...
Gamma-Ray Burst (GRB) afterglows are well described by synchrotron emission from relativistic blast waves expanding into an external medium. The wave is believed to amplify the magnetic field and accelerate electrons a power law distribution of energies promptly behind shock. These then cool both adiabatically emitting inverse Compton radiation. resulting spectra known consist several segments, which smoothly join at certain break frequencies. Here, we give complete description all possible...
We report on the observation of bright, long gamma-ray burst, GRB 090902B, by Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments on-board Fermi observatory. This was one brightest GRBs to have been observed LAT, which detected several hundred photons during prompt phase. With a redshift z = 1.822, this burst is among most luminous Fermi. Time-resolved spectral analysis reveals significant power-law component in LAT data that distinct from usual Band model emission seen...
We present detailed observations of the bright short-hard gamma-ray burst GRB 090510 made with Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) on board Fermi observatory. is first detected by LAT that shows strong evidence for a deviation from Band spectral fitting function during prompt emission phase. The time-integrated spectrum fit sum $\Epeak = 3.9\pm 0.3$\,MeV, which highest yet measured, hard power-law component photon index $-1.62\pm 0.03$ dominates below...
Short gamma-ray bursts (SGRBs) are among the most luminous explosions in universe, releasing less than one second energy emitted by our Galaxy over year. Despite decades of observations, nature their "central engine" remains unknown. Considering a binary magnetized neutron stars and solving Einstein equations, we show that merger results rapidly spinning black hole surrounded hot highly torus. Lasting 35 ms much longer previous simulations, study reveals magnetohydrodynamical instabilities...
In three years of observations since the beginning nominal science operations in August 2008, Large Area Telescope (LAT) on board Fermi Gamma Ray Space has observed high-energy (>20 MeV) \gamma-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 ~ 20 MeV. The first Fermi-LAT catalog is a compilation these detections provides systematic study for time. To generate catalog, we examined 733 by Gamma-Ray Burst Monitor (GBM) processed each...
The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by Large Area Telescope aboard Fermi Gamma-ray Space provide constraints on nature these unique astrophysical sources. GRB had largest fluence, highest-energy photon (95 GeV), longest γ-ray duration (20 hours), and one isotropic energy releases ever observed from a GRB. Temporal spectral analyses challenge widely accepted model that nonthermal high-energy emission in afterglow phase GRBs is synchrotron radiated...
Abstract We report the discovery of GRB 221009A, highest flux gamma-ray burst (GRB) ever observed by Fermi Gamma-ray Burst Monitor (Fermi-GBM). This has continuous prompt emission lasting more than 600 s, which smoothly transitions to afterglow visible in Fermi-GBM energy range (8 keV–40 MeV), and total energetics higher any other sample. By using a variety new existing analysis techniques we probe spectral temporal evolution 221009A. find no prior trigger time ( t 0 ; 2022 October 9 at...
Long-duration gamma-ray bursts (GRBs) are powerful cosmic explosions, signaling the death of massive stars. Among them, GRB 221009A is by far brightest burst ever observed. Because its enormous energy (Eiso ≈ 1055 erg) and proximity (z 0.15), an exceptionally rare event that pushes limits our theories. We present multiwavelength observations covering first 3 months afterglow evolution. The x-ray brightness decays as a power law with slope ≈t-1.66, which not consistent standard predictions...
Abstract Magnetar giant flares (MGFs) are the most energetic non-catastrophic transients known to originate from stellar objects. The first discovered events were nearby. In recent years, several extragalactic have been identified, implying an extremely high volumetric rate. We show that future instruments with a sensitivity ≲5 × 10 −9 erg cm −2 at ∼1 MeV will be dominated by MGFs over short gamma-ray bursts (sGRBs). Clear discrimination of requires intrinsic GRB localization capability...
The localization of the short-duration, hard-spectrum GRB 050509b was a watershed event. Thanks to nearly immediate relay position by Swift, we began imaging field 8 minutes after burst and continued for following days. No convincing optical/infrared candidate afterglow or supernova found object. We present re-analysis XRT find an absolute that is ~4" west reported previously. Close this bright elliptical galaxy with redshift z=0.2248, about 1' from center rich cluster galaxies. Based on...
We calculate gamma-ray burst (GRB) afterglow light curves from a relativistic jet as seen by observers at various viewing angles, θobs, relative to the axis. describe three increasingly more realistic models and compare resulting curves. An observer θobs < θ0, where θ0 is initial opening angle, should see curve very similar that for an on-axis observer. > sees rising early times, peaking when Lorentz factor ~1/θobs, approaching observer, later times. A strong linear polarization (≲40%) may...
We carry out a numerical hydrodynamical modeling for the evolution of relativistic collimated outflow as it interacts with surrounding medium and calculate light curve resulting from synchrotron emission shocked fluid. The hydrodynamic equations are reduced to one-dimensional by assuming axial symmetry integrating over radial profile flow, thus considerably reducing computation time. present results number different initial jet structures, including several power laws Gaussian dependence...
We report on the observation of bright, long gamma-ray burst, GRB 090926A, by Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments board \Fermi\ Space Telescope. 090926A shares several features with other bright LAT bursts. In particular, it clearly shows a short spike in light curve that is present all detectors see this turn suggests there common region emission across entire energy range. addition, while separate high-energy power-law component has already been...
We report on observations of GRB 080503, a short gamma-ray burst (GRB) with very bright extended emission (about 30 times the fluence initial spike) in conjunction thorough comparison to other Swift events. In spite prompt-emission brightness, however, optical counterpart is extraordinarily faint, never exceeding 25 mag deep starting at ∼1 hr after Burst Alert Telescope (BAT) trigger. The brightness peaks day and then falls sharply manner similar predictions Li & Paczyński (1998) for...
We analyze the MeV/GeV emission from four bright Gamma-Ray Bursts (GRBs) observed by Fermi-Large Area Telescope to produce robust, stringent constraints on a dependence of speed light in vacuo photon energy (vacuum dispersion), form Lorentz invariance violation (LIV) allowed some Quantum Gravity (QG) theories. First, we use three different and complementary techniques constrain total degree dispersion data. Additionally, using maximally conservative set assumptions possible source-intrinsic...
We present the observations of GRB090510 performed by Fermi Gamma-Ray Space Telescope and Swift observatory. This is a bright, short burst that shows an extended emission detected in GeV range. Furthermore, its optical initially rises, feature so far observed only long bursts, while X-ray flux initial shallow decrease, followed steeper decay. exceptional behavior enables us to investigate physical properties GRB outflow, poorly known bursts. discuss internal shock external models for...
The strong variability of magnetic central engines active galactic nuclei (AGNs) and gamma-ray bursts (GRBs) may result in highly intermittent strongly magnetized relativistic outflows. We find a new acceleration mechanism for such impulsive flows that can be much more effective than the steady-state flows. This results kinetic-energy-dominated are conducive to efficient dissipation at internal magnetohydrodynamic shocks on astrophysically relevant distances from source. For spherical flow,...
The X-ray to radio afterglow emission of GRB 170817A/GW 170817 so far scales as $F_ν\proptoν^{-0.6}t^{0.8}$ with observed frequency and time, consistent a single power-law segment the synchrotron spectrum from external shock going into ambient medium. This requires effective isotropic equivalent energy in visible region increase $\sim t^{1.7}$. two main channels for such an are (i) \emph{radial}: more carried by slower material (in region) gradually catches up energizes it, (ii)...
The short-duration ($\lesssim2\;$s) GRB 170817A in the nearby ($D=40\;$Mpc) elliptical galaxy NGC 4993 is first electromagnetic counterpart of gravitational wave (GW) detection a binary neutron-star (NS-NS) merger. It was followed by optical, IR, and UV emission from half day up to weeks after event, as well late time X-ray radio emission. early UV, IR showed quasi-thermal spectrum suggestive radioactive-decay powered kilonova-like Comparison kilonova models favors formation short-lived...