Thermonuclear Bursts with Short Recurrence Times from Neutron Stars Explained by Opacity-Driven Convection

Abstract

Thermonuclear flashes of hydrogen and helium accreted onto neutron stars produce the frequently observed Type I X-ray bursts. It is the current paradigm that almost all material burns in a burst, after which it takes hours to accumulate fresh fuel for the next burst. In rare cases, however, bursts are observed with recurrence times as short as minutes. We present the first one-dimensional multi-zone simulations that reproduce this phenomenon. Bursts that ignite in a relatively hot neutron star envelope leave a substantial fraction of the fuel unburned at shallow depths. In the wake of the burst, convective mixing events driven by opacity bring this fuel down to the ignition depth on the observed timescale of minutes. There, unburned hydrogen mixes with the metal-rich ashes, igniting to produce a subsequent burst. We find burst pairs and triplets, similar to the observed instances. Our simulations reproduce the observed fraction of bursts with short waiting times of ~30%, and demonstrate that short recurrence time bursts are typically less bright and of shorter duration.

arXiv comment11 pages, 15 figures, accepted for publication in ApJ

References in corpus (28)

• Nucleosynthesis in Massive Stars With Improved Nuclear and Stellar Physics
• Astrophysical Reaction Rates From Statistical Model Calculations
• Presupernova Evolution of Differentially Rotating Massive Stars Including Magnetic Fields
• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• Models for Type I X-Ray Bursts with Improved Nuclear Physics
• Mapping crustal heating with the cooling lightcurves of quasi-persistent transients
• Heating in the Accreted Neutron Star Ocean: Implications for Superburst Ignition
• Nuclear composition and heating in accreting neutron-star crusts
• Six years of BeppoSAX Wide Field Cameras observations of nine galactic type-I X-ray bursters
• Strong neutrino cooling by cycles of electron capture and ${\beta }^{-}$ decay in neutron star crusts
• Beyond Mixing-length Theory: a step toward 321D
• Spread of Matter over a Neutron-Star Surface During Disk Accretion: Deceleration of Rapid Rotation
• Hydrodynamic Models of Type I X-Ray Bursts: Metallicity Effects
• Millihertz quasi-periodic oscillations and thermonuclear bursts from Terzan 5: A showcase of burning regimes
• Multi-Instrument X-ray Observations of Thermonuclear Bursts with Short Recurrence Times
• A strong shallow heat source in the accreting neutron star MAXI J0556-332
• Quiescent thermal emission from neutron stars in LMXBs
• Discovery of X-ray burst triplets in EXO 0748-676
• Turbulent Mixing in the Surface Layers of Accreting Neutron Stars
• The effect of rotation on the stability of nuclear burning in accreting neutron stars
• Multi-Zone Models of Superbursts from Accreting Neutron Stars
• Multidimensional Modeling of Type I X-ray Bursts. I. Two-Dimensional Convection Prior to the Outburst of a Pure Helium Accretor
• Urca cooling pairs in the neutron star ocean and their effect on superbursts
• Reaction Rate and Composition Dependence of the Stability of Thermonuclear Burning on Accreting Neutron Stars
• The Second Born Corrections to the Electrical and Thermal Conductivities of Dense Matter in the Liquid Metal Phase
• Multidimensional Modeling of Type I X-ray Bursts. II. Two-Dimensional Convection in a Mixed H/He Accretor
• X-ray bursts and burst oscillations from the slowly spinning X-ray pulsar IGR J17480-2446 (Terzan 5)
• Convective overshoot mixing in stellar interior models

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• Influence of Nuclear Reaction Rate Uncertainties on Neutron Star Properties Extracted From X-ray Burst Model-Observation Comparisons
• Consistent Modeling of GS 1826-24 X-ray Bursts for Multiple Accretion Rates Demonstrates the Possibility to Constrain rp-process Reaction Rates
• Horizons: Nuclear Astrophysics in the 2020s and Beyond
• Multi-epoch X-ray burst modelling: MCMC with large grids of 1D simulations
• Localised thermonuclear bursts from accreting magnetic white dwarfs
• A cooling neutron star crust after recurrent outbursts: Modelling the accretion outburst history of Aql X-1
• NICER observes a secondary peak in the decay of a thermonuclear burst from 4U 1608-52
• The Galactic LMXB Population and the Galactic Centre Region
• Thermonuclear X-ray bursts in rapid succession in 4U 1636-536 with AstroSat-LAXPC
• The X-ray bursts of XTE J1739-285: a NICER sample
• Thermonuclear X-ray Bursts with late secondary peaks observed from 4U 1608-52
• Relativistic ocean $r$-modes during type-I X-ray bursts
• The efficiency of nuclear burning during thermonuclear (Type I) bursts as a function of accretion rate
• Nuclear-powered X-ray millisecond pulsars
• Discovery of transition from marginally stable burning to unstable burning after a superburst in Aql X-1
• Burning in the tail: implications for a burst oscillation model
• XMMU J181227.8-181234: a new ultracompact X-ray binary candidate
• The Impacts of Neutron-Star Structure and Base Heating on Type I X-Ray Bursts and Code Comparison
• Dynamics of Laterally Propagating Flames in X-ray Bursts. II. Realistic Burning & Rotation
• Hydrogen-triggered X-ray Bursts from SAX J1808.4-3658? The Onset of Nuclear Burning
• Thermal convection in rotating spherical shells: temperature-dependent internal heat generation using the example of triple-$\alpha$ burning in neutron stars
• Improved Nuclear Physics Near $A=61$ Refines Urca Neutrino Luminosities in Accreted Neutron Star Crusts
• Constraining Accreted Neutron Star Crust Shallow Heating with the Inferred Depth of Carbon Ignition in X-ray Superbursts
• The Great Wall: Urca Cooling Layers in the Accreted NS Crust
• NuSTAR and AstroSat observations of thermonuclear X-ray bursts with short-recurrence times in 4U 1636$-$536
• The onset of low Prandtl number thermal convection in thin spherical shells