Fallback Accretion Halted by R-process Heating in Neutron Star Mergers and Gamma-Ray Bursts

Abstract

The gravitational wave event GW170817 with a macronova/kilonova shows that a merger of two neutron stars ejects matter with radioactivity including $r$-process nucleosynthesis. A part of the ejecta inevitably falls back to the central object, possibly powering long-lasting activities of a short gamma-ray burst (sGRB), such as extended and plateau emissions. We investigate the fallback accretion with the $r$-process heating by performing one-dimensional hydrodynamic simulations and developing a semi-analytical model. We show that the usual fallback rate $dM/dt\propto t^{-5/3}$ is halted by the heating because pressure gradients accelerate ejecta beyond an escape velocity. The suppression is steeper than Chevalier's power-law model through Bondi accretion within a turn-around radius. The characteristic halting timescale is $\sim 10^5$--$10^9$ sec for the GW170817-like $r$-process heating, which is long enough to continue the long-lasting emission of sGRBs. The halting timescale is sensitive to the uncertainty of the $r$-process. Future observation of fallback halting could constrain the $r$-process heating on the year scale.

arXiv comment22 pages, 15 figures

References in corpus (70)

• 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
• The Burst Alert Telescope (BAT) on the Swift MIDEX Mission
• Origin of the heavy elements in binary neutron-star mergers from a gravitational wave event
• Electromagnetic Counterparts of Compact Object Mergers Powered by the Radioactive Decay of R-process Nuclei
• 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
• 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
• Gamma-ray Burst Afterglow with Continuous Energy Injection: Signature of a Highly-Magnetized Millisecond Pulsar
• Production of all the r-process nuclides in the dynamical ejecta of neutron star mergers
• Optical emission from a kilonova following a gravitational-wave-detected neutron-star merger
• Comprehensive nucleosynthesis analysis for ejecta of compact binary mergers
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. I. Dark Energy Camera Discovery of the Optical Counterpart
• The Combined Ultraviolet, Optical, and Near-Infrared Light Curves of the Kilonova Associated with the Binary Neutron Star Merger GW170817: Unified Data Set, Analytic Models, and Physical Implications
• 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
• Systematics of dynamical mass ejection, nucleosynthesis, and radioactively powered electromagnetic signals from neutron-star mergers
• Bright X-ray Flares in Gamma-Ray Burst Afterglows
• Signatures of magnetar central engines in short GRB lightcurves
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. III. Optical and UV Spectra of a Blue Kilonova From Fast Polar Ejecta
• Modeling GW170817 based on numerical relativity and its implications
• Short Duration Gamma-Ray Bursts with Extended Emission from Proto-Magnetar Spin-Down
• Dynamical Mass Ejection from Binary Neutron Star Mergers
• Delayed outflows from black hole accretion tori following neutron star binary coalescence
• Early Spectra of the Gravitational Wave Source GW170817: Evolution of a Neutron Star Merger
• Radioactivity and thermalization in the ejecta of compact object mergers and their impact on kilonova light curves
• Kilonova from post-merger ejecta as an optical and near-infrared counterpart of GW170817
• The r-process nucleosynthesis in the various jet-like explosions of magnetorotational core-collapse supernovae
• The Progenitors of Short Gamma-Ray Bursts
• A large scale dynamo and magnetoturbulence in rapidly rotating core-collapse supernovae
• Long-term GRMHD Simulations of Neutron Star Merger Accretion Disks: Implications for Electromagnetic Counterparts
• Electromagnetic Evidence that SSS17a is the Result of a Binary Neutron Star Merger
• Short GRBs with Extended Emission from Magnetar Birth: Jet Formation and Collimation
• An efficient shock-capturing central-type scheme for multidimensional relativistic flows. I. Hydrodynamics
• Dynamical mass ejection from black hole-neutron star binaries
• Fallback accretion in the aftermath of a compact binary merger
• Constraints on the ejecta of the GW170817 neutron-star merger from its electromagnetic emission
• Variabilities of Gamma-Ray Burst Afterglows: Long-acting Engine, Anisotropic Jet or Many Fluctuating Regions?
• Radiative transfer simulation for the optical and near-infrared electromagnetic counterparts to GW170817
• The Rapid Reddening and Featureless Optical Spectra of the optical counterpart of GW170817, AT 2017gfo, During the First Four Days
• 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
• Radioactive decay products in neutron star merger ejecta: heating efficiency and $\gamma$-ray emission
• R-Process Nucleosynthesis in MHD Jet Explosions of Core-Collapse Supernovae
• Sub-radian-accuracy gravitational waveforms of coalescing binary neutron stars in numerical relativity
• Kilonovae across the nuclear physics landscape: The impact of nuclear physics uncertainties on r-process-powered emission
• Modeling Kilonova Light Curves: Dependence on Nuclear Inputs
• Post-merger Mass Ejection of Low-mass Binary Neutron Stars
• Radioactive heating rate of r-process elements and macronova light curve
• The Diversity of Kilonova Emission in Short Gamma-Ray Bursts
• A supra-massive magnetar central engine for short GRB 130603B
• Constraints on long-lived remnants of neutron star binary mergers from late-time radio observations of short duration gamma-ray bursts
• A luminosity distribution for kilonovae based on short gamma-ray burst afterglows
• Jet Luminosity From Neutrino-Dominated Accretion Flows in Gamma-Ray Bursts
• Double Neutron Star Mergers and Short Gamma-Ray Bursts: Long-Lasting High-Energy Signatures and Remnant Dichotomy
• Radioactive Heating and Late Time Kilonova Light Curves
• Testing the Magnetar Model via Late Time Radio Observations of Two Macronova Candidates
• Spectral Puzzle of the Off-Axis Gamma-Ray Burst in GW170817
• Jet Propagation in Expanding Medium for Gamma-Ray Bursts
• A low-mass binary neutron star: long-term ejecta evolution and kilonovae with weak blue emission
• Bimodal Long-Lasting Components in Short Gamma-Ray Bursts: Promising Electromagnetic Counterparts to Neutron Star Binary Mergers
• Long-Lasting Black-Hole Jets in Short Gamma-Ray Bursts
• Continued radio observations of GW170817 3.5 years post-merger
• Imprints of r-process heating on fall-back accretion: distinguishing black hole-neutron star from double neutron star mergers
• Gravitational Collapse of Rotating Supermassive Stars including Nuclear Burning Effects
• Delayed X-ray emission from fallback in compact-object mergers
• Linking extended and plateau emissions of short gamma-ray bursts
• Exponentially Decaying Extended Emissions Following Short Gamma-Ray Bursts with Possible Luminosity -- E-folding Time Correlation
• Fallback Accretion Model for the Years-to-Decades X-ray Counterpart to GW170817

Cited by in corpus (8)

• Comprehensive study of mass ejection and nucleosynthesis in binary neutron star mergers leaving short-lived massive neutron stars
• Coalescence of black hole--neutron star binaries
• Self-consistent picture of the mass ejection from a one second-long binary neutron star merger leaving a short-lived remnant in general-relativistic neutrino-radiation magnetohydrodynamic simulation
• Estimating outflow masses and velocities in merger simulations: impact of r-process heating and neutrino cooling
• Dynamical ejecta of neutron star mergers with nucleonic weak processes II: Kilonova emission
• Cocoon breakout and escape from the ejecta of neutron star mergers
• Cocoon cooling emission in neutron star mergers
• Late-time accretion in neutron star mergers: implications for short gamma-ray bursts and kilonovae