The accretion rate dependence of burst oscillation amplitude

Abstract

Neutron stars in low mass X-ray binaries exhibit oscillations during thermonuclear bursts, attributed to asymmetric brightness patterns on the burning surfaces. All models that have been proposed to explain the origin of these asymmetries (spreading hotspots, surface waves, and cooling wakes) depend on the accretion rate. By analysis of archival RXTE data of six oscillation sources, we investigate the accretion rate dependence of the amplitude of burst oscillations. This more than doubles the size of the sample analysed previously by Muno et al. (2004), who found indications for a relationship between accretion rate and oscillation amplitudes. We find that burst oscillation signals can be detected at all observed accretion rates. Moreover, oscillations at low accretion rates are found to have relatively small amplitudes ($A_{\text{rms}}\le 0.10$) while oscillations detected in bursts observed at high accretion rates cover a broad spread in amplitudes ($0.05\le A_{\text{rms}}\le 0.20$). In this paper we present the results of our analysis and discuss these in the light of current burst oscillation models. Additionally, we investigate the bursts of two sources without previously detected oscillations. Despite that these sources have been observed at accretion rates where burst oscillations might be expected, we find their behaviour to be not anomalous compared to oscillation sources.

arXiv comment17 pages, 10 figures, accepted for publication in ApJ

References in corpus (35)

• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• Nuclear-Powered Millisecond Pulsars and the Maximum Spin Frequency of Neutron Stars
• Thermonuclear burst oscillations
• Propagation of thermonuclear flames on rapidly rotating neutron stars: extreme weather during type I X-ray bursts
• Discovery of coherent millisecond X-ray pulsations in Aql X-1
• Rotational Evolution During Type I X-Ray Bursts
• Dependence of the Frequency of the Kilohertz Quasi-Periodic Oscillations on X-ray Count Rate and Colors in 4U 1608-52
• XTE J1701-462 and its Implications for the Nature of Subclasses in Low-Magnetic-Field Neutron Star Low-Mass X-Ray Binaries
• Keplerian frequency of uniformly rotating neutron stars and quark stars
• A Chandra observation of the long-duration X-ray transient KS 1731-260 in quiescence: too cold a neutron star?
• Evidence for enhanced persistent emission during sub-Eddington thermonuclear bursts
• R-Modes on Rapidly Rotating, Relativistic Stars: I. Do Type-I Bursts Excite Modes in the Neutron-Star Ocean?
• The Amplitude Evolution and Harmonic Content of Millisecond Oscillations in Thermonuclear X-ray Bursts
• The Frequency Stability of Millisecond Oscillations in Thermonuclear X-Ray Bursts
• On the Frequency Evolution of X-ray Brightness Oscillations During Thermonuclear X-ray Bursts: Evidence for Coherent Oscillations
• Discovery of nearly coherent oscillations with a frequency of ~567 Hz during type-I X-ray bursts of the X-ray transient and eclipsing binary X 1658-298
• Surface Modes on Bursting Neutron Stars and X-ray Burst Oscillations
• Implications of burst oscillations from the slowly rotating accreting pulsar IGR 17480-2446 in the globular cluster Terzan 5
• Analysis of variability in the burst oscillations of the accreting millisecond pulsar XTE J1814-338
• Flame Propagation on the Surfaces of Rapidly Rotating Neutron Stars during Type I X-ray Bursts
• The Latitude of Type I X-Ray Burst Ignition on Rapidly Rotating Neutron Stars
• Ignition latitude and the shape of Type I X-ray bursts
• The Effect of Neutron Star Rotation on the Properties of Thermonuclear X-ray Bursts
• Rotational effects in thermonuclear Type I Bursts: equatorial crossing and directionality of flame spreading
• Neutron Star Crustal Interface Waves
• X-ray Burst Oscillations: From Flame Spreading to the Cooling Wake
• On the non-detection of gamma-rays from energetic millisecond pulsars -- dependence on viewing geometry
• Intermittent dipping in a low-mass X-ray Binary
• Coherence of burst oscillations and accretion-powered pulsations in the accreting millisecond pulsar XTE J1814-338
• Evidence of thermonuclear flame spreading on neutron stars from burst rise oscillations
• Fast and slow magnetic deflagration fronts in Type I X-ray bursts
• Evolution of the bursting-layer wave during a Type 1 X-ray burst
• Coherent oscillations and the evolution of the emission area in the decaying phase of radius-expansion bursts from 4U 1636-53
• Generation of Type I X-ray Burst Oscillations by Unstable Surface Modes
• Damping of Type I X-ray Burst Oscillations by Convection

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