Discovery of a Second Kilohertz QPO in the X-ray Binary 4U 1735-44

Abstract

In recent observations with the Rossi X-Ray Timing Explorer we have detected two simultaneous quasi-periodic oscillation (QPO) peaks in the low mass X-ray binary and atoll source 4U 1735-44. The lower and higher frequency QPOs have frequencies varying between 632 and 729 Hz, and 982 and 1026 Hz, respectively. The fractional rms amplitudes are 3.7 to 8.1% and 5.0 to 5.8%. The frequency separation between the two QPOs changes from 341+-7 Hz to 296+-12 Hz. The inferred mass accretion rate during our observations is relatively low compared to that during the previous observations, where only a single QPO was present. There is weak evidence that the frequency of the QPOs correlates with the mass accretion rate, as observed in other binaries. Five X-ray bursts were recorded with no detectable oscillations with upper limits for the rms fraction of 4% to 13%.

accepted by ApJ Letters, for more information see the QPO page at http://www.astro.uva.nl/ecford/qpos.html

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Cited by in corpus (30)

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• Dependence of the Frequency of the Kilohertz Quasi-Periodic Oscillations on X-ray Count Rate and Colors in 4U 1608-52
• RXTE observations of the neutron star low-mass X-ray binary GX 17+2: correlated X-ray spectral and timing behavior
• Precise Measurements of the Kilohertz Quasi-Periodic Oscillations in 4U 1728-34
• Relations Between Timing Features and Colors in the X-Ray Binary 4U 0614+09
• The distribution of kHz QPO frequencies in bright LMXBs
• Kilohertz QPOs in Neutron Star Binaries modeled as Keplerian Oscillations in a Rotating Frame of Reference
• On the nature of the compact star in 4U 1728-34
• Modelling the spin equilibrium of neutron stars in LMXBs without gravitational radiation
• Changing Frequency Separation of Kilohertz Quasi-Periodic Oscillations in the Sonic-Point Beat-Frequency Model
• The power spectral properties of the Z-source GX 340+0
• Low and high frequency variability as a function of spectral properties in the bright X-ray binary GX 5-1
• The MHD Alfven wave oscillation model of kHz Quasi Periodic Oscillations of Accreting X-ray Binaries
• On the maximum amplitude and coherence of the kilohertz quasi-periodic oscillations in low-mass X-ray binaries
• The correlations between the twin kHz QPO frequencies of LMXBs
• A self-consistent approach to the hard and soft states of 4U 1705-44
• Drop of coherence of the lower kilo-Hz QPO in neutron stars: is there a link with the innermost stable circular orbit?
• Investigation of the emission radii of kHz QPOs for the accreting millisecond X-Ray pulsars, Atoll and Z sources
• Quasi Periodic Oscillations in Low Mass X-Ray Binaries and Constraints on the Equation of State of Neutron Star Matter
• High-frequency variability in neutron-star low-mass X-ray binaries
• On the relativistic precession and oscillation frequencies of test particles around rapidly rotating compact stars
• Evolution of cross-correlation and time lag of 4U 1735-44 along the branches
• Statistical properties of twin kHz QPO in neutron star LMXBs
• Testing the transition layer model of quasi-periodic oscillations in neutron star X-ray binarie
• BeppoSAX and XMM-Newton spectral study of 4U 1735-44
• Probing the accretion disc structure by the twin kHz QPOs and spins of neutron stars in LMXBs
• Quasi Periodic Oscillations in X-ray Neutron Star and Probes of Perihelion Precession of General Relativity
• On The Low Frequency Quasi Periodic Oscillations of X-ray Sources
• Study on Correlations between the Twin Kilohertz Quasi-periodic Oscillations in Low-mass X-ray Binaries