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arXiv · 1804.03380

The Influence of Stellar Spin on Ignition of Thermonuclear Runaways

Duncan K. Galloway·Jean J. M. in 't Zand·Jérôme Chenevez·Laurens Keek·Celia Sanchez-Fernandez·Hauke Wörpel·Nathanael Lampe·Erik Kuulkers·Anna Watts·Laura Ootes
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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.

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Duncan K. Galloway, Jean J. M. in 't Zand, Jérôme Chenevez, Laurens Keek, Celia Sanchez-Fernandez, Hauke Wörpel, Nathanael Lampe, Erik Kuulkers, Anna Watts, Laura Ootes. 2018-04-10. The Influence of Stellar Spin on Ignition of Thermonuclear Runaways. https://doi.org/10.3847/2041-8213%2Faabd32

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