scholarly journals On the opening angle of magnetized jets from neutron-star mergers: the case of GRB170817A

2020 ◽  
Vol 495 (4) ◽  
pp. 3780-3787 ◽  
Author(s):  
Antonios Nathanail ◽  
Ramandeep Gill ◽  
Oliver Porth ◽  
Christian M Fromm ◽  
Luciano Rezzolla
Keyword(s):  
Neutron Star ◽  
Gamma Ray ◽  
Initial Conditions ◽  
Observation Angle ◽  
Opening Angle ◽  
Binary Neutron Star ◽  
Best Fitting ◽  
Standard Picture ◽  
General Relativistic ◽  
Star Binary

ABSTRACT The observations of GW170817/GRB170817A have confirmed that the coalescence of a neutron-star binary is the progenitor of a short gamma-ray burst (GRB). In the standard picture of a short GRB, a collimated highly relativistic outflow is launched after merger and it successfully breaks out from the surrounding ejected matter. Using initial conditions inspired from numerical-relativity binary neutron-star merger simulations, we have performed general-relativistic hydrodynamic (HD) and magnetohydrodynamic (MHD) simulations in which the jet is launched and propagates self-consistently. The complete set of simulations suggests that: (i) MHD jets have an intrinsic energy and velocity polar structure with a ‘hollow core’ subtending an angle θcore ≈ 4°–5° and an opening angle of θjet > ≳ 10°; (ii) MHD jets eject significant amounts of matter and two orders of magnitude more than HD jets; (iii) the energy stratification in MHD jets naturally yields the power-law energy scaling E(> Γβ) ∝ (Γβ)−4.5; (iv) MHD jets provide fits to the afterglow data from GRB170817A that are comparatively better than those of the HD jets and without free parameters; and (v) finally, both of the best-fitting HD/MHD models suggest an observation angle θobs ≃ 21° for GRB170817A.

scholarly journals 3D magnetized jet break-out from neutron-star binary merger ejecta: afterglow emission from the jet and the ejecta

2021 ◽  
Vol 502 (2) ◽  
pp. 1843-1855
Author(s):  
Antonios Nathanail ◽  
Ramandeep Gill ◽  
Oliver Porth ◽  
Christian M Fromm ◽  
Luciano Rezzolla
Keyword(s):  
Neutron Star ◽  
Thermal Emission ◽  
Opening Angle ◽  
Hollow Core ◽  
Binary Neutron Star ◽  
Vlbi Observations ◽  
Superluminal Motion ◽  
General Relativistic ◽  
Star Binary ◽  
Magnetohydrodynamic Simulations

ABSTRACT We perform 3D general-relativistic magnetohydrodynamic simulations to model the jet break-out from the ejecta expected to be produced in a binary neutron-star merger. The structure of the relativistic outflow from the 3D simulation confirms our previous results from 2D simulations, namely, that a relativistic magnetized outflow breaking out from the merger ejecta exhibits a hollow core of θcore ≈ 4°, an opening angle of θjet ≳ 10°, and is accompanied by a wind of ejected matter that will contribute to the kilonova emission. We also compute the non-thermal afterglow emission of the relativistic outflow and fit it to the panchromatic afterglow from GRB170817A, together with the superluminal motion reported from VLBI observations. In this way, we deduce an observer angle of $\theta _{\rm obs}= 35.7^{\circ \, \, +1.8}_{\phantom{\circ \, \, }-2.2}$. We further compute the afterglow emission from the ejected matter and constrain the parameter space for a scenario in which the matter responsible for the thermal kilonova emission will also lead to a non-thermal emission yet to be observed.

scholarly journals Gamma-Ray Bursts and Binary Neutron Star Mergers

1996 ◽  
Vol 165 ◽  
pp. 489-502
Author(s):  
Tsvi Piran
Keyword(s):  
Neutron Star ◽  
Gravitational Radiation ◽  
Gamma Ray ◽  
Indirect Evidence ◽  
Gamma Ray Bursts ◽  
Binary Neutron Star ◽  
Merger Event ◽  
Γ Rays ◽  
Γ Ray ◽  
The One

Neutron star binaries, such as the one observed in the famous binary pulsar PSR 1913+16, end their life in a catastrophic merger event (denoted here NS2M). The merger releases ∼5 1053 ergs, mostly as neutrinos and gravitational radiation. A small fraction of this energy suffices to power γ-ray bursts (GRBs) at cosmological distances. Cosmological GRBs must pass, however, an optically thick fireball phase and the observed γ rays emerge only at the end of this phase. Hence, it is difficult to determine the nature of the source from present observations (the agreement between the rates of GRBs and NS2Ms providing only indirect evidence for this model). In the future a coinciding detection of a GRB and a gravitational-radiation signal could confirm this model.

scholarly journals Binary Neutron Star (BNS) Merger: What We Learned from Relativistic Ejecta of GW/GRB 170817A

Physics ◽  
2019 ◽  
Vol 1 (2) ◽  
pp. 194-228 ◽  
Author(s):  
Houri Ziaeepour
Keyword(s):  
Neutron Star ◽  
Gravitational Waves ◽  
Gamma Ray ◽  
Lorentz Factor ◽  
Prompt Gamma ◽  
External Shocks ◽  
Binary Neutron Star ◽  
Tidal Forces ◽  
Relativistic Jet ◽  
Short Grbs

Gravitational Waves (GW) from coalescence of a Binary Neutron Star (BNS) and its accompanying short Gamma-Ray Burst (GRB) GW/GRB 170817A confirmed the presumed origin of these puzzling transients and opened up the way for relating properties of short GRBs to those of their progenitor stars and their surroundings. Here we review an extensive analysis of the prompt gamma-ray and late afterglows of this event. We show that a fraction of polar ejecta from the merger had been accelerated to ultra-relativistic speeds. This structured jet had an initial Lorentz factor of about 260 in our direction, which was O ( 10 ∘ ) from the jet’s axis, and was a few orders of magnitude less dense than in typical short GRBs. At the time of arrival to circum-burst material the ultra-relativistic jet had a close to Gaussian profile and a Lorentz factor ≳ 130 in its core. It had retained in some extent its internal collimation and coherence, but had extended laterally to create mildly relativistic lobes—a cocoon. Its external shocks on the far from center inhomogeneous circum-burst material and low density of colliding shells generated slowly rising afterglows, which peaked more than 100 days after the prompt gamma-ray. The circum-burst material was somehow correlated with the merger. As non-relativistic outflows or tidally ejected material during BNS merger could not have been arrived to the location of the external shocks before the relativistic jet, circum-burst material might have contained recently ejected materials from resumption of internal activities, faulting and mass loss due to deformation and breaking of stars crusts by tidal forces during latest stages of their inspiral but well before their merger. By comparing these findings with the results of relativistic Magneto-Hydro-Dynamics (MHD) simulations and observed gravitational waves we conclude that progenitor neutron stars were most probably old, had close masses and highly reduced magnetic fields.

scholarly journals Jet Propagation in Neutron Star Mergers and GW170817

2019 ◽  
Author(s):  
Hamid Hamidani ◽  
Kenta Kiuchi ◽  
Kunihito Ioka
Keyword(s):  
Neutron Star ◽  
Numerical Simulations ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Expansion Velocity ◽  
Analytic Model ◽  
Binary Neutron Star ◽  
Central Engine ◽  
Relativistic Jet ◽  
Wave Event

Abstract The gravitational wave event from the binary neutron star (BNS) merger GW170817 and the following multi-messenger observations present strong evidence for i) merger ejecta expanding with substantial velocities and ii) a relativistic jet which had to propagate through the merger ejecta. The ejecta’s expansion velocity is not negligible for the jet head motion, which is a fundamental difference from the other systems like collapsars and active galactic nuclei. Here we present an analytic model of the jet propagation in an expanding medium. In particular, we notice a new term in the expression of the breakout time and velocity. In parallel, we perform a series of over a hundred 2D numerical simulations of jet propagation. The BNS merger ejecta is prepared based on numerical relativity simulations of a BNS merger with the highest-resolution to date. We show that our analytic results agree with numerical simulations over a wide parameter space. Then we apply our analytic model to GW170817, and obtain two solid constraints on: i) the central engine luminosity as Liso, 0 ∼ 3 × 1049 − 2.5 × 1052 erg s−1, and on ii) the delay time between the merger and engine activation t0 − tm < 1.3 s. The engine power implies that the apparently-faint short gamma-ray burst (sGRB) sGRB 170817A is similar to typical sGRBs if observed on-axis.

scholarly journals General relativistic simulations of magnetized binary neutron star mergers

2008 ◽  
Vol 78 (2) ◽  
Author(s):  
Yuk Tung Liu ◽  
Stuart L. Shapiro ◽  
Zachariah B. Etienne ◽  
Keisuke Taniguchi
Keyword(s):  
Neutron Star ◽  
Binary Neutron Star ◽  
General Relativistic

scholarly journals NECESSARY CONDITIONS FOR SHORT GAMMA-RAY BURST PRODUCTION IN BINARY NEUTRON STAR MERGERS

2014 ◽  
Vol 788 (1) ◽  
pp. L8 ◽  
Author(s):  
Ariadna Murguia-Berthier ◽  
Gabriela Montes ◽  
Enrico Ramirez-Ruiz ◽  
Fabio De Colle ◽  
William H. Lee
Keyword(s):  
Neutron Star ◽  
Gamma Ray ◽  
Necessary Conditions ◽  
Gamma Ray Burst ◽  
Binary Neutron Star

scholarly journals Exploring Binary-Neutron-Star-Merger Scenario of Short-Gamma-Ray Bursts by Gravitational-Wave Observation

2010 ◽  
Vol 104 (14) ◽  
Author(s):  
Kenta Kiuchi ◽  
Yuichiro Sekiguchi ◽  
Masaru Shibata ◽  
Keisuke Taniguchi
Keyword(s):  
Neutron Star ◽  
Gravitational Wave ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Binary Neutron Star ◽  
Wave Observation

scholarly journals General Relativistic Simulations of Binary Neutron Star Mergers

2011 ◽  
Author(s):  
Bruno Giacomazzo ◽  
Luciano Rezzolla ◽  
Luca Baiotti ◽  
David Link ◽  
José A. Font ◽  
...  
Keyword(s):  
Neutron Star ◽  
Binary Neutron Star ◽  
General Relativistic
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