Electromagnetic emission of white dwarf binary mergers

Abstract

It has been recently proposed that the ejected matter from white dwarf (WD) binary mergers can produce transient, optical and infrared emission similar to the "kilonovae" of neutron star (NS) binary mergers. To confirm this we calculate the electromagnetic emission from WD-WD mergers and compare with kilonova observations. We simulate WD-WD mergers leading to a massive, fast rotating, highly magnetized WD with an adapted version of the smoothed-particle-hydrodynamics (SPH) code Phantom. We thus obtain initial conditions for the ejecta such as escape velocity, mass and initial position and distribution. The subsequent thermal and dynamical evolution of the ejecta is obtained by integrating the energy-conservation equation accounting for expansion cooling and a heating source given by the fallback accretion onto the newly-formed WD and its magneto-dipole radiation. We show that magnetospheric processes in the merger can lead to a prompt, short gamma-ray emission of up to $\approx 10^{46}$ erg in a timescale of $0.1$-$1$ s. The bulk of the ejecta initially expands non-relativistically with velocity $0.01c$ and then it accelerates to $0.1c$ due to the injection of fallback accretion energy. The ejecta become transparent at optical wavelengths around $\sim 7$ days post-merger with a luminosity $10^{41}$-$10^{42}$ erg s${}^{-1}$. The X-ray emission from the fallback accretion becomes visible around $\sim 150$-$200$ day post-merger with a luminosity of $10^{39}$ erg s${}^{-1}$. We also predict the post-merger time at which the central WD should appear as a pulsar depending on the value of the magnetic field and rotation period.

arXiv comment12 pages, Accepted for publication in JCAP

References in corpus (29)

• Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A
• Atomic Data for Astrophysics. II. New Analytic Fits for Photoionization Cross Sections of Atoms and Ions
• An Ordinary Short Gamma-Ray Burst with Extraordinary Implications: Fermi-GBM Detection of GRB 170817A
• 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
• SPLASH: An interactive visualisation tool for Smoothed Particle Hydrodynamics simulations
• 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. III. Optical and UV Spectra of a Blue Kilonova From Fast Polar Ejecta
• Kilonovae
• Phantom: A smoothed particle hydrodynamics and magnetohydrodynamics code for astrophysics
• The Binary Neutron Star event LIGO/VIRGO GW170817 a hundred and sixty days after merger: synchrotron emission across the electromagnetic spectrum
• Rates and Delay Times of Type Ia Supernovae
• Optical and X-ray emission from stable millisecond magnetars formed from the merger of binary neutron stars
• Prelude to a double degenerate merger: the onset of mass transfer and its impact on gravitational waves and surface detonations
• Fallback accretion in the aftermath of a compact binary merger
• The structure and fate of white dwarf merger remnants
• Double degenerate mergers as progenitors of high-field magnetic white dwarfs
• The Coalescence Rate of Double Neutron Star Systems
• Remnants of Binary White Dwarf Mergers
• The separation distribution and merger rate of double white dwarfs: improved constraints
• The Post-Merger Magnetized Evolution of White Dwarf Binaries: The Double-Degenerate Channel of Sub-Chandrasekhar Type Ia Supernovae and the Formation of Magnetized White Dwarfs
• On general relativistic uniformly rotating white dwarfs
• SGRs and AXPs as rotation powered massive white dwarfs
• A Parameter-Space Study of Carbon-Oxygen White Dwarf Mergers
• Magnetized Moving Mesh Merger of a Carbon-Oxygen White Dwarf Binary
• The binary fraction, separation distribution, and merger rate of white dwarfs from SPY
• Lithium production in the merging of white dwarf stars
• GRB 170817A-GW170817-AT 2017gfo and the observations of NS-NS, NS-WD and WD-WD mergers
• The Spin Evolution of Fast-Rotating, Magnetized Super-Chandrasekhar White Dwarfs in the Aftermath of White Dwarf Mergers

Cited by in corpus (15)

• The formation of neutron star systems through accretion-induced collapse in white-dwarf binaries
• GRB-SN Association within the Binary-Driven Hypernova Model
• Induced Gravitational Collapse, Binary-Driven Hypernovae, Long Gramma-ray Bursts and Their Connection with Short Gamma-ray Bursts
• Orbital decay of double white dwarfs: beyond gravitational wave radiation effects
• X-ray photolysis of CH${}_3$COCH${}_3$ ice: Implications for the radiation effects of compact objects towards astrophysical ices
• Rotating white dwarf models with finite-temperature envelope
• The double white dwarf merger progenitors of SDSS J2211+1136 and ZTF J1901+1458
• Time evolution of rotating and magnetized white dwarf stars
• On the optical transients from double white-dwarf mergers
• A Brief Review of Binary Driven Hypernova
• Astrophysics with the Laser Interferometer Space Antenna
• The white dwarf binary merger model of GRB 170817A
• A half-ring of ionized circumstellar material trapped in the magnetosphere of a white dwarf merger remnant
• Revealing Double White Dwarf Mergers with Multi-messenger Signals
• Optical transients from non-explosive double white-dwarf mergers: the case of a central neutron star remnant