Reaction Rate and Composition Dependence of the Stability of Thermonuclear Burning on Accreting Neutron Stars

Abstract

The stability of thermonuclear burning of hydrogen and helium accreted onto neutron stars is strongly dependent on the mass accretion rate. The burning behavior is observed to change from Type I X-ray bursts to stable burning, with oscillatory burning occurring at the transition. Simulations predict the transition at a ten times higher mass accretion rate than observed. Using numerical models we investigate how the transition depends on the hydrogen, helium, and CNO mass fractions of the accreted material, as well as on the nuclear reaction rates of triple alpha and the hot-CNO breakout reactions 15O(a,g)19Ne and 18Ne(a,p)21Na. For a lower hydrogen content the transition is at higher accretion rates. Furthermore, most experimentally allowed reaction rate variations change the transition accretion rate by at most 10%. A factor ten decrease of the 15O(a,g)19Ne rate, however, produces an increase of the transition accretion rate of 35%. None of our models reproduce the transition at the observed rate, and depending on the true 15O(a,g)19Ne reaction rate, the actual discrepancy may be substantially larger. We find that the width of the interval of accretion rates with marginally stable burning depends strongly on both composition and reaction rates. Furthermore, close to the stability transition, our models predict that X-ray bursts have extended tails where freshly accreted fuel prolongs nuclear burning.

12 pages, 14 figures. Submitted for publication in ApJ

References in corpus (10)

• Modelling the behaviour of accretion flows in X-ray binaries
• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• The Effects of Variations in Nuclear Processes on Type I X-Ray Burst Nucleosynthesis
• Models of Type I X-ray Bursts from GS 1826-24: A Probe of rp-Process Hydrogen Burning
• First superburst from a classical low-mass X-ray binary transient
• Superburst Models for Neutron Stars with Hydrogen and Helium-Rich Atmospheres
• Millihertz Oscillation Frequency Drift Predicts the Occurrence of Type I X-ray Bursts
• The ${}^{15}$O($\alpha$,$\gamma$)${}^{19}$Ne Breakout Reaction and Impact on X-Ray Bursts
• Turbulent Mixing in the Surface Layers of Accreting Neutron Stars
• The superburst recurrence time in luminous persistent LMXBs

Cited by in corpus (16)

• Dependence of X-Ray Burst Models on Nuclear Reaction Rates
• The Multi-INstrument Burst ARchive (MINBAR)
• Thermonuclear Bursts with Short Recurrence Times from Neutron Stars Explained by Opacity-Driven Convection
• Constraints on Bygone Nucleosynthesis of Accreting Neutron Stars
• Millihertz quasi-periodic oscillations in 4U 1636-53 associated with bursts with positive convexity only
• Discovery of a correlation between the frequency of the mHz quasi-periodic oscillations and the neutron-star temperature in the low-mass X-ray binary 4U 1636-53
• Thermonuclear X-ray Bursts with late secondary peaks observed from 4U 1608-52
• The efficiency of nuclear burning during thermonuclear (Type I) bursts as a function of accretion rate
• On the dependence of X-ray burst rate on accretion and spin rate
• The Thermal Stability of Helium Burning on Accreting Neutron Stars
• Phase-resolved analyses of mHz quasi-periodic oscillations in 4U 1636-53 using Hilbert-Huang transform
• Quasi periodic whispers from a transient ULX in M\,101: signatures of a fast-spinning neutron star?
• XMM-Newton and NICER measurement of the rms spectrum of the millihertz quasi-periodic oscillations in the neutron-star low-mass X-ray binary 4U 1636-53
• The harmonic component of the millihertz quasi-periodic oscillations in 4U 1636-53
• A solution to the tension of burning on neutron stars and nuclear physics
• Quasi-periodic pulse amplitude modulation in the accreting millisecond pulsar IGR J00291+5934