GW170817 4.5 years after merger: Dynamical ejecta afterglow constraints

Abstract

GW170817 is the first binary neutron star (NS) merger detected in gravitational waves (GWs) and photons, and so far remains the only GW event of its class with a definitive electromagnetic (EM) counterpart. Radio emission from the structured jet associated with GW170817 has faded below the sensitivity achievable via deep radio observations with the most sensitive radio arrays currently in operation. Hence, we now have the opportunity to probe the radio re-brightening that some models predict, should emerge at late times from the interaction of the dynamically-stripped merger ejecta with the interstellar medium. Here we present the latest results from our deep radio observations of the GW170817 field with the Karl G. Jansky Very Large Array (VLA), 4.5 years after the merger. Our new data at $3$GHz do not show any compelling evidence for emission in excess to the tail of the jet afterglow ($<3.3\mu$Jy), confirming our previous results. We thus set new constraints on the dynamical ejecta afterglow models. These constraints favor single-speed ejecta with energy $\lesssim 10^{50}$erg (for an ejecta speed of ${\beta }_0=0.5$), or steeper energy-speed distributions of the kilonova ejecta. Our results also suggest larger values of the cold, non-rotating maximum NS mass in equal mass scenarios. However, without a detection of the dynamical ejecta afterglow, obtaining precise constraints on the NS equation of state remains challenging.

6 pages, 5 figures. Published in ApJ

References in corpus (32)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A
• Origin of the heavy elements in binary neutron-star mergers from a gravitational wave event
• 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
• Spectroscopic identification of r-process nucleosynthesis in a double neutron star merger
• The X-ray counterpart to the gravitational wave event GW 170817
• A kilonova as the electromagnetic counterpart to a gravitational-wave source
• Light Curves of the Neutron Star Merger GW170817/SSS17a: Implications for R-Process Nucleosynthesis
• Illuminating Gravitational Waves: A Concordant Picture of Photons from a Neutron Star Merger
• The Emergence of a Lanthanide-Rich Kilonova Following the Merger of Two Neutron Stars
• Optical emission from a kilonova following a gravitational-wave-detected neutron-star merger
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. IV. Detection of Near-infrared Signatures of r-process Nucleosynthesis with Gemini-South
• A Radio Counterpart to a 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
• 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
• Electromagnetic Evidence that SSS17a is the Result of a Binary Neutron Star Merger
• A Deep Chandra X-ray Study of Neutron Star Coalescence GW170817
• Mass ejection from neutron star mergers: different components and expected radio signals
• 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
• Radio Constraints on Long-Lived Magnetar Remnants in Short Gamma-Ray Bursts
• Continued radio observations of GW170817 3.5 years post-merger
• Observable Features of GW170817 Kilonova Afterglow
• Dynamical ejecta synchrotron emission as possible contributor to the changing behaviour of GRB170817A
• Searching for the radio remnants of short duration gamma-ray bursts
• Shock within a shock: revisiting the radio flares of NS merger ejecta and GRB-supernovae
• Constraining the long-lived magnetar remnants in short gamma-ray bursts from late-time radio observations
• Constraining the Jet Launching Time of GRB 170817A by Utilizing the Baryon Loading
• Late-time radio observations of the short GRB200522A: constraints on the magnetar model
• Search for radio remnants of nearby off-axis Gamma-Ray Bursts in a sample of Swift/BAT events
• Deep ATCA and VLA radio observations of short-GRB host galaxies. Constraints on star-formation rates, afterglow flux, and kilonova radio flares

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• LOFAR observations of gravitational wave merger events: O3 results and O4 strategy
• Follow-up of Neutron Star Mergers with CTA and Prospects for Joint Detection with Gravitational-Wave Detectors
• RADAR-Radio Afterglow Detection and AI-driven Response: A Federated Framework for Gravitational Wave Event Follow-Up
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• The non-thermal emission following GW170817 is consistent with a conical radially-stratified outflow with initial Lorentz factor $\lesssim 10$
• The Detection Prospect of the Counter Jet Radiation in the Late Afterglow of GRB 170817A