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Binary Neutron Star (BNS) Merger: What We Learned from Relativistic Ejecta of GW/GRB 170817A
- Source :
- MDPI Physics, MDPI Physics, 2019, 1 (2), pp.194-228. ⟨10.3390/physics1020018⟩
- Publication Year :
- 2019
- Publisher :
- HAL CCSD, 2019.
-
Abstract
- Gravitational waves from coalescence of a Binary Neutron Star (BNS) and its accompagning short Gamma-Ray Burst GW/GRB~170817A confirmed the presumed origin of these puzzeling 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 - $\mathcal{O}(10^\circ)$ 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 $\gtrsim 130$ in its core. It had retained in some extent its internal collimation and coherence, but had extended laterally to create mildly relativistic lobes - a {\it cocoon}. External shocks on the far from center inhomogeneous circum-burst material and low density of colliding shells generated slow rising afterglows. The circum-burst material was somehow correlated with the merger and it is possible that it contained recently ejected material from glitching, which had resumed due to the deformation of neutron stars crust by tidal forces in the latest stages of inspiral but well before their merger. By comparing these findings with the results of relativistic MHD simulations and observed gravitational waves we conclude that progenitor neutron stars were old, had close masses and highly reduced magnetic fields. In addition, they probably had oppositely directed spins due to the encounter and gravitational interaction with other stars.<br />Comment: 30 pages; 11 figures. Invited review for special issue "Multimessenger Probes of the Universe", MDPI-Physics
- Subjects :
- Astrophysics::High Energy Astrophysical Phenomena
FOS: Physical sciences
gamma-ray burst
Astrophysics
Astrophysics::Cosmology and Extragalactic Astrophysics
01 natural sciences
symbols.namesake
0103 physical sciences
Tidal force
010306 general physics
Ejecta
010303 astronomy & astrophysics
gravitational wave
Astrophysics::Galaxy Astrophysics
Physics
High Energy Astrophysical Phenomena (astro-ph.HE)
Gravitational wave
Stars
Neutron star
Lorentz factor
symbols
Magnetohydrodynamics
Astrophysics - High Energy Astrophysical Phenomena
Gamma-ray burst
[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
binary neutron star merger
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Journal :
- MDPI Physics, MDPI Physics, 2019, 1 (2), pp.194-228. ⟨10.3390/physics1020018⟩
- Accession number :
- edsair.doi.dedup.....d7311355240ddc9b92faf1b99b91e262