Evidence for Antipodal Hot Spots During X-ray Bursts From 4U 1636-536

Abstract

The discovery of high-frequency brightness oscillations in thermonuclear X-ray bursts from several neutron-star low-mass X-ray binaries has important implications for the beat frequency model of kilohertz quasi-periodic brightness oscillations, the propagation of nuclear burning, the structure of the subsurface magnetic fields in neutron stars, and the equation of state of high-density matter. These implications depend crucially on whether the observed frequency is the stellar spin frequency or its first overtone. Here we report an analysis of five bursts from 4U 1636-536 which exhibit strong oscillations at approximately 580 Hz. We show that combining the data from the first 0.75 seconds of each of the five bursts yields a signal at 290 Hz that is significant at the $4\times 10^{-5}$ level when the number of trials is taken into account. This strongly indicates that 290 Hz is the spin frequency of this neutron star and that 580 Hz is its first overtone, in agreement with other arguments about this source but in contrast to suggestions in the literature that 580 Hz is the true spin frequency. The method used here, which is an algorithm for combining time series data from the five bursts so that the phases of the 580 Hz oscillations are aligned, may be used in any source to search for weak oscillations that have frequencies related in a definite way to the frequency of a strong oscillation.

9 pages including one figure, uses aaspp4.sty, submitted to The Astrophysical Journal Letters on September 18

References in corpus (7)

• Correlation Between Energy Spectral States and Fast Time Variability and Further Evidence for the Marginally Stable Orbit in 4U 1820-30
• Bounds on the Compactness of Neutron Stars from Brightness Oscillations
• On the Amplitude of Burst Oscillations in 4U 1636-54: Evidence for Nuclear Powered Pulsars
• Discovery of a second kHz QPO peak in 4U 1608-52
• Milli-second Oscillations in the Persistent and Bursting Flux of Aql X-1 During an Outburst
• Difference Frequency of Kilohertz QPOs Not Equal to Half the Burst Oscillation Frequency in 4U 1636-53
• The Long Term Stability of Oscillations During Thermonuclear X-ray Bursts: Constraining the Binary X-ray Mass Function

Cited by in corpus (38)

• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• Millisecond Oscillations in X-Ray Binaries
• Propagation of thermonuclear flames on rapidly rotating neutron stars: extreme weather during type I X-ray bursts
• Rotational Evolution During Type I X-Ray Bursts
• The Multi-INstrument Burst ARchive (MINBAR)
• Evidence for a Millisecond Pulsar in 4U 1636-53 During a Superburst
• Crust-core coupling and r-mode damping in neutron stars: a toy model
• Determining neutron star masses and radii using energy-resolved waveforms of X-ray burst oscillations
• X-ray time variability across the atoll source states of 4U 1636--53
• Nearly Coherent Oscillations in Type I X-Ray Bursts from KS 1731-260
• The Amplitude Evolution and Harmonic Content of Millisecond Oscillations in Thermonuclear X-ray Bursts
• R-Modes on Rapidly Rotating, Relativistic Stars: I. Do Type-I Bursts Excite Modes in the Neutron-Star Ocean?
• Millisecond Oscillations and Photospheric Radius Expansion in Thermonuclear X-Ray Bursts
• Changing Frequency Separation of Kilohertz Quasi-Periodic Oscillations in the Sonic-Point Beat-Frequency Model
• Is there a link between the neutron-star spin and the frequency of the kilohertz quasi-periodic oscillations?
• On the Magnetospheric Beat-Frequency and Lense-Thirring Interpretations of the Horizontal Branch Oscillation in the Z Sources
• 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
• Oscillation Waveforms and Amplitudes from Hot Spots on Neutron Stars
• Discovery of a 270 Hz X-Ray Burst Oscillation in the X-Ray Dipper 4U 1916-053
• An Atlas of Burst Oscillations and Spectral Properties in 4U 1728-34
• Bounds on Compactness for LMXB Neutron Stars from X-ray Burst Oscillations
• KiloHertz quasi-periodic oscillations difference frequency exceeds inferred spin frequency in 4U 1636-53
• Oscillations During Thermonuclear X-ray Bursts
• A uniform search for thermonuclear burst oscillations in the RXTE legacy dataset
• The Energy Dependence of Millisecond Oscillations in Thermonuclear X-ray Bursts
• Spin Down of Pulsations in the Cooling Tail of an X-ray Burst from 4U 1636-53
• Rayleigh - Taylor Gravity Waves and Quasiperiodic Oscillation Phenomenon in X-ray Binaries
• The Effect of the Mass Accretion Rate on the Burst Oscillations in 4U 1728-34
• Constraints on the Steady-State R-mode Amplitude in Neutron Star Transients
• Kilohertz quasi-periodic oscillations in low mass X-ray binary sources and their relation with the neutron star magnetic field
• Evidence for Harmonic Content and Frequency Evolution of Oscillations during the Rising Phase of X-ray Bursts from 4U 1636-536
• A Characterization of the Brightness Oscillations During Thermonuclear Bursts From 4U 1636-536
• Nuclear-powered X-ray millisecond pulsars
• Probing the Properties of Neutron Stars with Type-I X-Ray Bursts
• Recent Observations of X-Ray Emission from Galactic Binary Neutron Stars
• Gravity Waves from Rotating Neutron Stars and Evaluation of Fast Chirp Transform Techniques
• Large frequency drifts during Type I X-ray bursts
• QPO signatures of disk restoration after type-I X-ray bursts from 4U~1636$-$536