GW170817 Afterglow Reveals that Short Gamma-Ray Bursts are Neutron Star Mergers

Abstract

We systematically investigate the outflow structure of GW170817 in comparison with a sample of 27 cosmological short GRBs by modelling their afterglow light curves. We find that cosmological short GRBs share the same outflow structures with GW170817, relativistic structured jets. The jet opening angle of GW170817 is $6.3_{-0.6}^{+1.1}{}^{\circ }$, which is consistent with that of cosmological short GRBs (${\theta }_0=6.9^{\circ }\pm 2.3^{\circ }$). Our analysis indicates that GW170817 is viewed off-axis (${\theta }_{\mathrm{obs}}=30_{-4}^{+7}{}^{\circ }$), while cosmological short GRBs are viewed on-axis (${\theta }_{\mathrm{obs}}\lesssim {\theta }_0$). The exceptional properties of the GW170817 afterglow can be explained by the difference in observation angle alone. We demonstrate that the light curves of the GW170817 afterglow, if viewed on-axis, are consistent with those of cosmological short GRBs. Other properties of GW170817, such as Lorentz factor $\Gamma \approx 150$, spectral index $p\approx 2.15$, isotropic equivalent energy $E_{\mathrm{iso}}\approx 8\times 10^{52}$ erg and interstellar medium density $n_0\approx 10^{-2}$ proton cm${}^{-3}$, fit well within the ranges of those of cosmological short GRBs. The similarity between the GW170817 outflow structure and those of cosmological short GRBs indicates that cosmological short GRBs are likely neutron star mergers.

References in corpus (22)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• An Ordinary Short Gamma-Ray Burst with Extraordinary Implications: Fermi-GBM Detection of GRB 170817A
• 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
• Illuminating Gravitational Waves: A Concordant Picture of Photons from a Neutron Star Merger
• A Radio Counterpart to a Neutron Star Merger
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. V. Rising X-ray Emission from an Off-Axis Jet
• Compact radio emission indicates a structured jet was produced by a binary neutron star merger
• 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
• A Deep Chandra X-ray Study of Neutron Star Coalescence GW170817
• Electromagnetic Counterparts to Structured Jets from Gravitational Wave Detected Mergers
• The optical afterglow of GW170817 at one year post-merger
• A Strong Jet Signature in the Late-Time Lightcurve of GW170817
• A long-lived neutron star merger remnant in GW170817: constraints and clues from X-ray observations
• Off-axis short GRBs from structured jets as counterparts to GW events
• Brightening X-ray Emission from GW170817/GRB170817A: Further Evidence for an Outflow
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. VIII. A Comparison to Cosmological Short-duration Gamma-ray Bursts
• Gamma Ray Bursts Are Observed Off-Axis
• A lesson from GW170817: most neutron star mergers result in tightly collimated successful GRB jets
• Electrons' energy in GRB afterglows implied by radio peaks
• Observational constraints on the structure of gamma-ray burst jets
• Constraining the Outflow Structure of the Binary Neutron Star Merger Event GW170817 with Markov-Chain Monte Carlo Analysis

Cited by in corpus (40)

• Kilonovae
• Two years of non-thermal emission from the binary neutron star merger GW170817: rapid fading of the jet afterglow and first constraints on the kilonova fastest ejecta
• The structure of hydrodynamic $\gamma$-ray burst jets
• Searching for Electromagnetic Counterparts to Gravitational-wave Merger Events with the Prototype Gravitational-wave Optical Transient Observer (GOTO-4)
• The Optical Afterglow of GW170817: An Off-axis Structured Jet and Deep Constraints on a Globular Cluster Origin
• Tight multi-messenger constraints on the neutron star equation of state from GW170817 and a forward model for kilonova light curve synthesis
• Evidence for X-ray Emission in Excess to the Jet Afterglow Decay 3.5 yrs After the Binary Neutron Star Merger GW 170817: A New Emission Component
• A Search for Neutron Star-Black Hole Binary Mergers in the Short Gamma-Ray Burst Population
• Inclination Dependence of Kilonova Light Curves from Globally Aspherical Geometries
• 3D magnetised jet break-out from neutron-star binary merger ejecta: afterglow emission from the jet and the ejecta
• GRMHD simulations of neutron-star mergers with weak interactions: r-process nucleosynthesis and electromagnetic signatures of dynamical ejecta
• Afterglow constraints on the viewing angle of binary neutron star mergers and determination of the Hubble constant
• Robust Features of Off-Axis Gamma-Ray Burst Afterglow Lightcurves
• The Gravity Collective: A Search for the Electromagnetic Counterpart to the Neutron Star-Black Hole Merger GW190814
• Gravitational-wave Merger Forecasting: Scenarios for the early detection and localization of compact-binary mergers with ground based observatories
• Constraining short gamma-ray burst jet properties with gravitational waves and gamma rays
• AT 2018cow VLBI: No Long-Lived Relativistic Outflow
• The Effect of Jet-Ejecta Interaction on the Viewing Angle Dependence of Kilonova Light Curves
• A search for prompt gamma-ray counterparts to fast radio bursts in the Insight-HXMT data
• Deep Hubble Space Telescope Observations of GW170817: Complete Light Curves and the Properties of the Galaxy Merger of NGC 4993
• Modeling Synchrotron Self-Compton and Klein-Nishina Effects in Gamma-Ray Burst Afterglows
• From Neutrino- to Photon-Cooled in Three Years: Can Fallback Accretion Explain the X-ray Excess in GW170817?
• jetsimpy: A Highly Efficient Hydrodynamic Code for Gamma-ray Burst Afterglow
• Analytic Model for Off-Axis GRB Afterglow Images -- Geometry Measurement and Implications for Measuring $H_0$
• Counting on Short Gamma-Ray Bursts: Gravitational-Wave Constraints of Jet Geometry
• The jet structure and the intrinsic luminosity function of short gamma-ray bursts
• Constraining the long-lived supramassive neutron stars by magnetar boosted kilonovae
• Constraining Delay Time Distribution of Binary Neutron Star Mergers from Host Galaxy Properties
• Radio Afterglows from Compact Binary Coalescences: Prospects for Next-Generation Telescopes
• Constraining properties of neutron star merger outflows with radio observations
• The Panchromatic Afterglow of GW170817: The full uniform dataset, modeling, comparison with previous results and implications
• Potential biases and prospects for the Hubble constant estimation via electromagnetic and gravitational-wave joint analyses
• Prospects of calibrating afterglow modeling of short GRBs with gravitational wave inclination angle measurements and resolving the Hubble tension with a GW-GRB association event
• Joint analysis of gravitational-wave and electromagnetic data of mergers: breaking an afterglow model degeneracy in GW170817 and in future events
• Neutron conversion-diffusion: a new model for structured short gamma-ray burst jets compatible with GRB 170817
• Insights into Binary Neutron Star Merger Simulations: A Multi-Code Comparison
• How Do Nuclear Isomers Influence the Gamma-Ray Bursts in Binary Neutron Star Mergers?
• Perspectives for multi-messenger astronomy with the next generation of gravitational-wave detectors and high-energy satellites
• The non-thermal emission following GW170817 is consistent with a conical radially-stratified outflow with initial Lorentz factor $\lesssim 10$
• Host galaxies and electromagnetic counterparts to binary neutron star mergers across the cosmic time: Detectability of GW170817-like events