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 this.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2018
- DOI:
- 10.3847/2041-8213/aabd32
- arXiv:
- arXiv:1804.03380
- Bibcode:
- 2018ApJ...857L..24G
- Keywords:
-
- nuclear reactions;
- nucleosynthesis;
- abundances;
- stars: neutron;
- stars: rotation;
- X-rays: bursts;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 9 pages, 2 figures