Fast and slow magnetic deflagration fronts in Type I X-ray bursts

Abstract

Type I X-ray bursts are produced by thermonuclear runaways that develop on accreting neutron stars. Once one location ignites, the flame propagates across the surface of the star. Flame propagation is fundamental in order to understand burst properties like rise time and burst oscillations. Previous work quantified the effects of rotation on the front, showing that the flame propagates as a deflagration and that the front strongly resembles a hurricane. However the effect of magnetic fields was not investigated, despite the fact that magnetic fields strong enough to have an effect on the propagating flame are expected to be present on many bursters. In this paper we show how the coupling between fluid layers introduced by an initially vertical magnetic field plays a decisive role in determining the character of the fronts that are responsible for the Type I bursts. In particular, on a star spinning at 450 Hz (typical among the bursters) we test seed magnetic fields of $10^7-10^{10}$ G and find that for the medium fields the magnetic stresses that develop during the burst can speed up the velocity of the burning front, bringing the simulated burst rise time close to the observed values. By contrast, in a magnetic slow rotator like IGR J17480--2446, spinning at 11 Hz, a seed field $\gtrsim 10^9$ G is required to allow localized ignition and the magnetic field plays an integral role in generating the burst oscillations observed during the bursts.

Pubblished on MNRAS

References in corpus (3)

• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• The magnetic field strengths of accreting millisecond pulsars
• Rotational effects in thermonuclear Type I Bursts: equatorial crossing and directionality of flame spreading

Cited by in corpus (18)

• Thermonuclear X-ray bursts
• Nuclear Physics of the Outer Layers of Accreting Neutron Stars
• Constraining the Properties of the Thermonuclear Burst Oscillation Source XTE J1814-338 Through Pulse Profile Modelling
• Multi-epoch X-ray burst modelling: MCMC with large grids of 1D simulations
• The accretion rate dependence of burst oscillation amplitude
• On the dependence of X-ray burst rate on accretion and spin rate
• Relativistic ocean $r$-modes during type-I X-ray bursts
• Nuclear-powered X-ray millisecond pulsars
• Dynamics of Laterally Propagating Flames in X-ray Bursts. I. Burning Front Structure
• Three-dimensional instability of flame fronts in type I X-ray bursts
• Pulse Profile Modelling of Thermonuclear Burst Oscillations II: Handling variability
• Dynamics of Laterally Propagating Flames in X-ray Bursts. II. Realistic Burning & Rotation
• Toward Resolved Simulations of Burning Fronts in Thermonuclear X-ray Bursts
• Thermal convection in rotating spherical shells: temperature-dependent internal heat generation using the example of triple-$\alpha$ burning in neutron stars
• Superburst oscillations: ocean and crustal modes excited by Carbon-triggered Type I X-ray bursts
• Comparing Early Evolution of Flames in X-ray Bursts in Two and Three Dimensions
• The onset of low Prandtl number thermal convection in thin spherical shells
• Thermonuclear burst oscillations and the dense matter equation of state