Constraining the ejecta for the nonthermal emission from GW170817

Abstract

We consider a simple model for the nonthermal emission from GW170817, in which a quasi-spherical ejecta is released in the merger event, with the kinetic energy distributed over the momentum as $E(>\gamma \beta )\propto (\gamma \beta {)}^{-k}$. The ejecta drives a shock into the medium and gives rise to synchrotron radiation. Using multi-band observations we constrain that $k\approx 6.7$; (assuming medium density of $\sim 10^{-2}\mathrm{c}{\mathrm{m}}^{-3}$ and postshock magnetic field carries a fraction $10^{-5}-10^{-3}$ of the postshock internal energy) the total kinetic energy is $(0.3-5)\times 10^{51}$erg; the slowest ejecta velocity is $\sim (0.7-0.8)c$; and the fastest ejecta has a Lorentz factor of $\sim 4-7$. We conclude that the sub-relativistic dynamical ejecta responsible to the kilonova cannot produce the nonthermal emission. The co-existence of the nonthermal and thermal kilonova emission implies that two corresponding ejecta are ejected at different angles.

arXiv comment6 pages, 4 figures and 1 table, accepted for publication in ApJ

References in corpus (37)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Multi-messenger Observations of a Binary Neutron Star Merger
• Spectra and Light Curves of Gamma-Ray Burst Afterglows
• An Ordinary Short Gamma-Ray Burst with Extraordinary Implications: Fermi-GBM Detection of GRB 170817A
• Swope Supernova Survey 2017a (SSS17a), the Optical Counterpart to a Gravitational Wave Source
• Short-Duration Gamma-Ray Bursts
• Spectroscopic identification of r-process nucleosynthesis in a double neutron star merger
• INTEGRAL Detection of the First Prompt Gamma-Ray Signal Coincident with the Gravitational Wave Event GW170817
• The X-ray counterpart to the gravitational wave event GW 170817
• Optical emission from a kilonova following a gravitational-wave-detected neutron-star merger
• Swift and NuSTAR observations of GW170817: detection of a blue kilonova
• Particle acceleration by ultra-relativistic shocks: theory and simulations
• A Radio Counterpart to a Neutron Star Merger
• A Decade of Short-duration Gamma-ray Burst Broad-band Afterglows: Energetics, Circumburst Densities, and Jet Opening Angles
• Physical parameters of GRB 970508 and GRB 971214 from their afterglow synchrotron emission
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. V. Rising X-ray Emission from an Off-Axis Jet
• A mildly relativistic wide-angle outflow in the neutron star merger GW170817
• Late time afterglow observations reveal a collimated relativistic jet in the ejecta of the binary neutron star merger GW170817
• The Binary Neutron Star event LIGO/VIRGO GW170817 a hundred and sixty days after merger: synchrotron emission across the electromagnetic spectrum
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. VI. Radio Constraints on a Relativistic Jet and Predictions for Late-Time Emission from the Kilonova Ejecta
• Particle acceleration at ultrarelativistic shocks: an eigenfunction method
• The outflow structure of GW170817 from late time broadband observations
• Energy spectra of cosmic rays accelerated at ultrarelativistic shock waves
• A Deep Chandra X-ray Study of Neutron Star Coalescence GW170817
• A cocoon shock breakout as the origin of the $\gamma$-ray emission in GW170817
• The evolution of the X-ray afterglow emission of GW 170817 / GRB 170817A in XMM-Newton observations
• Magnetic Fields In Relativistic Collisionless Shocks
• The Distance to NGC 4993: The Host Galaxy of the Gravitational-wave Event GW170817
• The environment of the binary neutron star merger GW170817
• A turnover in the radio light curve of GW170817
• The spectrum of particles accelerated in relativistic, collisionless shocks
• Brightening X-ray Emission from GW170817/GRB170817A: Further Evidence for an Outflow
• A Neutron Star Binary Merger Model for GW170817/GRB170817a/SSS17a
• Implications of the radio and X-ray emission that followed GW170817
• Gamma-Ray Burst Afterglows from Realistic Fireballs
• On the magnetization of gamma-ray burst blast waves
• Constraining the magnetic field in GRB relativistic collisionless shocks using radio data

Cited by in corpus (2)

• Interpreting GRB170817A as a giant flare from a jet-less double neutron-star merger
• The afterglow emission from a stratified jet in GRB 170817A