Breaking stress of neutron star crust

Abstract

The breaking stress (the maximum of the stress-strain curve) of neutron star crust is important for neutron star physics including pulsar glitches, emission of gravitational waves from static mountains, and flares from star quakes. We perform many molecular dynamic simulations of the breaking stress at different coupling parameters (inverse temperatures) and strain rates. We describe our results with the Zhurkov model of strength. We apply this model to estimate the breaking stress for timescales ~1 s - 1 year, which are most important for applications, but much longer than can be directly simulated. At these timescales the breaking stress depends strongly on the temperature. For coupling parameter <200, matter breaks at very small stress, if it is applied for a few years. This viscoelastic creep can limit the lifetime of mountains on neutron stars. We also suggest an alternative model of timescale-independent breaking stress, which can be used to estimate an upper limit on the breaking stress.Comment: 5 pages, 2 figures. Accepted for publication in MNRAS Letter

A Survey of the Parameter Space of the Compressible Liquid Drop Model as Applied to the Neutron Star Inner Crust

“…The shear modulus of a Coulomb lattice of positively charged nuclei in a uniform negatively charged background in the NS crust at a baryon number density n b was determined through Monte Carlo simulation (Ogata & Ichimaru 1990;Strohmayer et al 1991;Chugunov & Horowitz 2010) and can be written as…”

“…The maximum and typical size of mountains on NS crusts Haskell et al 2006) and frequencies of torsional crustal oscillations (Piro 2005;Steiner & Watts 2009;Samuelsson & Andersson 2007;Andersson et al 2009) depends on the thickness of the elastically rigid part of the crust and its shear modulus, which depends on the characteristic quantities which define the lattice: the inter-ion spacing a and nuclear charge Z (Gearheart et al 2011). The shear modulus throughout the inner crust (Ogata & Ichimaru 1990;Strohmayer et al 1991;Chugunov & Horowitz 2010) is an important quantity in determining the frequencies at which the crust might undergo global oscillations. Various transport properties within the crust will also depend somewhat on the crustal composition through the densities of the various components, the electron fraction and the lattice spacing.…”

Transport Properties of the Nuclear Pasta Phase with Quantum Molecular Dynamics

“…The pasta phase has been studied extensively by static methods such as liquid-drop models [9,[11][12][13], Thomas-Fermi approximations [14,15], and the Hartee-Fock method [16,17] as well as using dynamical approaches like classical [3,4,6,[19][20][21][22][23][24][25] and quantum molecular dynamics simulations [28][29][30][31][32][33][34][35][36] and the time-dependent Hartree-Fock method [26,27]. Although several authors [8,[37][38][39] have studied transport properties of the crust, very few studies employed dynamical approach.…”

Magnetar Outbursts From Avalanches of Hall Waves and Crustal Failures

“…the crust must yield inelastically, as demonstrated in numerical experiments by Horowitz & Kadau (2009) and Chugunov & Horowitz (2010). They propose that σ cr depends on temperature as…”