Ignition latitude and the shape of Type I X-ray bursts

Abstract

The shape of the lightcurve during the rising phase of Type I X-ray bursts is determined by many factors including the ignition latitude, the accretion rate, and the rotation rate of the star. We develop a phenomenological model of the burst rise process and show that simple measures of the burst morphology can be robust diagnostics of ignition latitude and burning regime. We apply our results to the large sample of bursts from the Low Mass X-ray Binary 4U 1636-536, and find evidence for off-equatorial ignition for many of the bursts. We argue that such behaviour may be associated with the transition from hydrogen to helium ignition at accretion rates a few percent of Eddington. We show that this model can also explain variations in the detectability of burst oscillations, and discuss the implications for other burst sources.

Some additions and clarifications, MNRAS accepted

References in corpus (11)

• Neutron Star Observations: Prognosis for Equation of State Constraints
• Pulse profiles of millisecond pulsars and their Fourier amplitudes
• The Oblate Schwarzschild Approximation for Light Curves of Rapidly Rotating Neutron Stars
• Sedimentation and Type I X-ray Bursts at Low Accretion Rates
• Detection of the Irradiated Donor in the LMXBs 4U 1636-536 (=V801 Ara) and 4U 1735-444 (=V926 Sco)
• The Latitude of Type I X-Ray Burst Ignition on Rapidly Rotating Neutron Stars
• Signature of Temporary Burning Front Stalling from a Non-Photospheric Radius Expansion Double-peaked Burst
• The energy dependence of burst oscillations from the accreting millisecond pulsar XTE J1814-338
• Spreading of thermonuclear flames on the neutron star in SAX J1808.4-3658: an observational tool
• Thermonuclear Flame Spreading on Rapidly Spinning Neutron Stars: Indications of the Coriolis Force?
• Accretion rate and the occurrence of multi-peaked X-ray bursts

Cited by in corpus (15)

• Universality of the Acceleration Due to Gravity on the Surface of a Rapidly Rotating Neutron Star
• Influence of Nuclear Reaction Rate Uncertainties on Neutron Star Properties Extracted From X-ray Burst Model-Observation Comparisons
• Coherence of burst oscillations and accretion-powered pulsations in the accreting millisecond pulsar XTE J1814-338
• The accretion rate dependence of burst oscillation amplitude
• Evidence of thermonuclear flame spreading on neutron stars from burst rise oscillations
• The X-ray bursts of XTE J1739-285: a NICER sample
• Millihertz quasi-periodic oscillations in 4U 1636-53 associated with bursts with positive convexity only
• Detecting gravitational waves from accreting neutron stars
• Phase-resolved analyses of mHz quasi-periodic oscillations in 4U 1636-53 using Hilbert-Huang transform
• Detection of millihertz quasi-periodic oscillations in the low-mass X-ray binary 4U 1730--22 with NICER
• The thermonuclear X-ray bursts of 4U 1730-22
• XMM-Newton and NICER measurement of the rms spectrum of the millihertz quasi-periodic oscillations in the neutron-star low-mass X-ray binary 4U 1636-53
• New insight into the hard X-ray emission influenced by the type-\uppercase\expandafter{\romannumeral1} bursts observed by Insight-HXMT during outburst of 4U 1636--536
• Damping of Type I X-ray Burst Oscillations by Convection
• Time and energy dependent characteristics of Thermonuclear burst oscillations