ALMA and GMRT constraints on the off-axis gamma-ray burst 170817A from the binary neutron star merger GW170817

Abstract

Binary neutron-star mergers (BNSMs) are among the most readily detectable gravitational-wave (GW) sources with LIGO. They are also thought to produce short $\gamma$-ray bursts (SGRBs), and kilonovae that are powered by r-process nuclei. Detecting these phenomena simultaneously would provide an unprecedented view of the physics during and after the merger of two compact objects. Such a Rosetta Stone event was detected by LIGO/Virgo on 17 August 2017 at a distance of $\sim 44$ Mpc. We monitored the position of the BNSM with ALMA at 338.5 GHz and GMRT at 1.4 GHz, from 1.4 to 44 days after the merger. Our observations rule out any afterglow more luminous than $3\times 10^{26}{\mathrm{erg}\mathrm{s}}^{-1}{\mathrm{Hz}}^{-1}$ in these bands, probing $>$2--4 dex fainter than previous SGRB limits. We match these limits, in conjunction with public data announcing the appearance of X-ray and radio emission in the weeks after the GW event, to templates of off-axis afterglows. Our broadband modeling suggests that GW170817 was accompanied by a SGRB and that the GRB jet, powered by $E_{\mathrm{AG},\mathrm{iso}}\sim 10^{50}$~erg, had a half-opening angle of $\sim 20^{\circ }$, and was misaligned by $\sim 41^{\circ }$ from our line of sight. The data are also consistent with a more collimated jet: $E_{\mathrm{AG},\mathrm{iso}}\sim 10^{51}$~erg, ${\theta }_{1/2,\mathrm{jet}}\sim 5^{\circ }$, ${\theta }_{\mathrm{obs}}\sim 17^{\circ }$. This is the most conclusive detection of an off-axis GRB afterglow and the first associated with a BNSM-GW event to date. Assuming a uniform top-hat jet, we use the viewing angle estimates to infer the initial bulk Lorentz factor and true energy release of the burst.

Accepted for publication in the Astrophysical Journal Letter. 12 pages, 4 figures

References in corpus (20)

• 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
• An Ordinary Short Gamma-Ray Burst with Extraordinary Implications: Fermi-GBM Detection of GRB 170817A
• 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
• A kilonova as the electromagnetic counterpart to a gravitational-wave source
• The Emergence of a Lanthanide-Rich Kilonova Following the Merger of Two Neutron Stars
• Swift and NuSTAR observations of GW170817: detection of a blue kilonova
• A Radio Counterpart to a Neutron Star Merger
• Discerning the physical origins of cosmological Gamma-ray bursts based on multiple observational criteria: the cases of z=6.7 GRB 080913, z=8.3 GRB 090423, and some short/hard GRBs
• 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
• A Deep Chandra X-ray Study of Neutron Star Coalescence GW170817
• The Distance to NGC 4993: The Host Galaxy of the Gravitational-wave Event GW170817
• The environment of the binary neutron star merger GW170817
• A complete sample of bright Swift short Gamma-Ray Bursts
• Rise and fall of the X-ray flash 080330: an off-axis jet?
• The Unprecedented Properties of the First Electromagnetic Counterpart to a Gravitational Wave Source

Cited by in corpus (12)

• Radio Properties of Tidal Disruption Events
• Improved constraints on H0 from a combined analysis of gravitational-wave and electromagnetic emission from GW170817
• The First Short GRB Millimeter Afterglow: The Wide-Angled Jet of the Extremely Energetic SGRB 211106A
• Determine the Lorentz factor and the viewing angle of GRB 170817A
• Short duration gamma-ray bursts and their outflows in light of GW170817
• The luminosity functions of kilonovae from binary neutron star mergers under different equation of states
• VLT/MUSE and ATCA observations of the host galaxy of the short GRB 080905A at z=0.122
• The white dwarf binary merger model of GRB 170817A
• RADAR-Radio Afterglow Detection and AI-driven Response: A Federated Framework for Gravitational Wave Event Follow-Up
• Follow-up of Neutron Star Mergers with CTA and Prospects for Joint Detection with Gravitational-Wave Detectors
• Light curves and polarizations of gravitationally lensed kilonovae
• Deep ATCA and VLA radio observations of short-GRB host galaxies. Constraints on star-formation rates, afterglow flux, and kilonova radio flares