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 Worpel, Nathanael Lampe, Erik Kuulkers, Anna Watts, Laura Ootes

*Corresponding author for this work

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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 this.
Original languageEnglish
Article numberL24
JournalAstrophysical Journal Letters
Volume857
Issue number2
Number of pages6
ISSN2041-8205
DOIs
Publication statusPublished - 2018

Keywords

  • Nuclear reactions
  • Nucleosynthesis
  • Abundances
  • Stars: neutron
  • Stars: rotation
  • X-rays: bursts

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Cite this

Galloway, D. K., In't Zand, J. J. M., Chenevez, J., Keek, L., Sanchez-Fernandez, C., Worpel, H., Lampe, N., Kuulkers, E., Watts, A., & Ootes, L. (2018). The Influence of Stellar Spin on Ignition of Thermonuclear Runaways. Astrophysical Journal Letters, 857(2), [L24 ]. https://doi.org/10.3847/2041-8213/aabd32