The Latitude of Type I X-Ray Burst Ignition on Rapidly Rotating Neutron Stars

Abstract

We investigate the latitude at which type I X-ray bursts are ignited on rapidly rotating accreting neutron stars. We find that, for a wide range of accretion rates, ignition occurs preferentially at the equator, in accord with the work of Spitkovsky et al. However, for a range of accretion rates below the critical rate above which bursts cease, ignition occurs preferentially at higher latitudes. The range of accretion rates over which nonequatorial ignition occurs is an increasing function of the neutron star spin frequency. These findings have significant implications for thermonuclear flame propagation, and they may explain why oscillations during the burst rise are detected predominantly when the accretion rate is high. They also support the suggestion of Bhattacharyya & Strohmayer that non-photospheric radius expansion double-peaked bursts and the unusual harmonic content of oscillations during the rise of some bursts result from ignition at or near a rotational pole.

4 pages, 2 figures, accepted by ApJL

References in corpus (2)

• Signature of Temporary Burning Front Stalling from a Non-Photospheric Radius Expansion Double-peaked Burst
• Spreading of thermonuclear flames on the neutron star in SAX J1808.4-3658: an observational tool

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• The accretion rate dependence of burst oscillation amplitude
• Millihertz quasi-periodic oscillations in 4U 1636-53 associated with bursts with positive convexity only
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• Relativistic ocean $r$-modes during type-I X-ray bursts
• Accretion rate and the occurrence of multi-peaked X-ray bursts
• Phase-resolved analyses of mHz quasi-periodic oscillations in 4U 1636-53 using Hilbert-Huang transform
• The study of multi-peaked type-I X-ray bursts in the neutron-star low mass X-ray binary 4U 1636$-$536 with RXTE
• Damping of Type I X-ray Burst Oscillations by Convection
• Time and energy dependent characteristics of Thermonuclear burst oscillations