The Influence of Stellar Spin on Ignition of Thermonuclear Runaways

Abstract

Runaway thermonuclear burning of a layer of accumulated fuel on the surface of a compact star provides a brief but intense display of stellar nuclear processes. For neutron stars accreting from a binary companion, these events manifest as thermonuclear (type-I) X-ray bursts, and recur on typical timescales of hours to days. We measured the burst rate as a function of accretion rate, from seven neutron stars with known spin rates, using a burst sample accumulated over several decades. At the highest accretion rates, the burst rate is lower for faster spinning stars. The observations imply that fast (> 400 Hz) rotation encourages stabilization of nuclear burning, suggesting a dynamical dependence of nuclear ignition on the spin rate. This dependence is unexpected, because faster rotation entails less shear between the surrounding accretion disk and the star. Large-scale circulation in the fuel layer, leading to enhanced mixing of the burst ashes into the fuel layer, may explain this behavior; further numerical simulations are required to confirm.

arXiv comment9 pages, 2 figures; accepted for publication by Astrophysical Journal Letters

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Cited by in corpus (11)

• The Multi-INstrument Burst ARchive (MINBAR)
• Discovery of thermonuclear (Type I) X-ray bursts in the X-ray binary Swift J1858.6-0814 observed with NICER and NuSTAR
• NICER observations of the evidence of Poynting-Robertson drag and disk reflection during type I X-ray bursts from 4U 1636$-$536
• The efficiency of nuclear burning during thermonuclear (Type I) bursts as a function of accretion rate
• Discovery of transition from marginally stable burning to unstable burning after a superburst in Aql X-1
• Detection of Millihertz Quasi-Periodic Oscillations in the X-Ray Binary 1RXS J180408.9$-$342058
• The thermonuclear X-ray bursts of 4U 1730-22
• A solution to the tension of burning on neutron stars and nuclear physics
• Connecting the m-dots: accretion rates and thermonuclear burst recurrence times on neutron stars and white dwarfs
• Return of the Clocked Burster: Exceptionally Short Recurrence Time in GS 1826-238
• Nuclear astrophysics