Subsequent Nonthermal Emission due to the Kilonova Ejecta in GW 170817

Abstract

The ejected material at the binary neutron star merger GW 170817 was confirmed as a kilonova by UV, optical, and IR observations. This event provides a unique opportunity to investigate the particle acceleration at a mildly relativistic shock propagating in the circumbinary medium. In this paper, we simulate the nonthermal emission from electrons accelerated by the shock induced by the kilonova ejecta with a time-dependent method. The initial velocity and mass of the ejecta in the simulations are obtained from the kilonova observations in GW 170817. If the ambient density is high enough ($\geq 10^{-2}~\mbox{cm}^{-3}$), radio, optical/IR, and X-ray signals will be detected in a few years, though the off-axis short gamma-ray burst models, accounting for the X-ray/radio counterpart detected at $\sim 10$ days after the merger, implies low ambient density. We also demonstrate that the additional low-mass ($\sim 10^{-5}{M}_{\odot }$) component with a velocity of $0.5c$--$0.8c$ can reproduce the early X-ray/radio counterpart. This alternative model allows a favorably high density to detect the nonthermal emission due to the kilonova ejecta. Even for a low ambient density such as $\sim 10^{-3}~\mbox{cm}^{-3}$, depending on the microscopic parameters for the electron acceleration, we can expect a growth of radio flux of $\sim 0.1$ mJy in a few years.

5 pages, 5 figures, ApJ in press

References in corpus (19)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Multi-messenger Observations of a Binary Neutron Star Merger
• Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A
• Swope Supernova Survey 2017a (SSS17a), the Optical Counterpart to a Gravitational Wave Source
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. II. UV, Optical, and Near-IR Light Curves and Comparison to Kilonova Models
• The X-ray counterpart to the gravitational wave event GW 170817
• A kilonova as the electromagnetic counterpart to a gravitational-wave source
• Illuminating Gravitational Waves: A Concordant Picture of Photons from a Neutron Star Merger
• Optical emission from a kilonova following a gravitational-wave-detected neutron-star merger
• The discovery of the electromagnetic counterpart of GW170817: kilonova AT 2017gfo/DLT17ck
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. V. Rising X-ray Emission from an Off-Axis Jet
• Kilonova from post-merger ejecta as an optical and near-infrared counterpart of GW170817
• 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
• Mass ejection from neutron star mergers: different components and expected radio signals
• Brightening X-ray Emission from GW170817/GRB170817A: Further Evidence for an Outflow
• A Neutron Star Binary Merger Model for GW170817/GRB170817a/SSS17a
• Distance and properties of NGC 4993 as the host galaxy of a gravitational wave source, GW170817
• Temporal Evolution of the Gamma-ray Burst Afterglow Spectrum for an Observer: GeV--TeV Synchrotron Self-Compton Light Curve
• Simulations of gamma-ray burst afterglows with a relativistic kinetic code

Cited by in corpus (1)

• Fallback Accretion Model for the Years-to-Decades X-ray Counterpart to GW170817