RossiXTE monitoring of 4U 1636-53: I. Long-term evolution and kHz Quasi-Periodic Oscillations

Abstract

We have monitored the atoll-type neutron star low-mass X-ray binary 4U 1636-53 with the Rossi X-Ray Timing Explorer (RXTE) for more than 1.5 years. Our campaign consisted of short (~2 ks) pointings separated by two days, regularly monitoring the spectral and timing properties of the source. During the campaign we observed a clear long-term oscillation with a period of ~30-40 days, already seen in the light curves from the RXTE All-Sky Monitor, which corresponded to regular transitions between the hard (island) and soft (banana) states. We detected kHz QPOs in about a third of the observations, most of which were in the soft (banana) state. The distribution of the frequencies of the peak identified as the lower kHz QPO is found to be different from that previously observed in an independent data set. This suggests that the kHz QPOs in the system shows no intrinsically preferred frequency.

7 pages, 6 figures, accepted for publication on MNRAS

References in corpus (4)

• The coherence of kHz quasi-periodic oscillations in the X-rays from accreting neutron stars
• On the maximum amplitude and coherence of the kilohertz quasi-periodic oscillations in low-mass X-ray binaries
• On the kHz QPO frequency correlations in bright neutron star X-ray binaries
• Supporting evidence for the signature of the innermost stable circular orbit in Rossi X-ray data from 4U1636-536

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• Mass-angular-momentum relations implied by models of twin peak quasi-periodic oscillations
• Super-spinning compact objects and models of high-frequency quasi-periodic oscillations observed in Galactic microquasars
• The reflection spectrum of the low-mass X-ray binary 4U 1636-53
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• Thermonuclear X-ray bursts from LMXB 4U 1636$-$536 observed with AstroSat
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• Relation between the properties of the kilohertz quasi-periodic oscillations and spectral parameters in 4U 1636$-$53
• Constraining models of twin peak quasi-periodic oscillations with realistic neutron star equations of state
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• Broad iron emission line and kilohertz quasi-periodic oscillations in the neutron star system 4U 1636-53
• Mass and spin measurements for the neutron star 4U1608-52 through the relativistic precession model
• Parallel tracks as quasi-steady states for the magnetic boundary layers in neutron-star low-mass X-ray binaries
• A new correlation with lower kilohertz quasi-periodic oscillation frequency in the ensemble of low-mass X-ray binaries
• Fast variability from X-ray binaries
• QPO signatures of disk restoration after type-I X-ray bursts from 4U~1636$-$536