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- Title
Statistical properties of twin kilohertz quasi-periodic oscillations in neutron star low-mass X-ray binaries.
- Authors
Wang, D. H.; Chen, L.; Zhang, C. M.; Lei, Y. J.; Qu, J. L.
- Abstract
We collect the data of twin kilohertz quasi-periodic oscillations (kHz QPOs) published before 2012 from 26 neutron star (NS) low-mass X-ray binary (LMXB) sources, then we analyze the centroid frequency ( ν) distribution of twin kHz QPOs (lower frequency ν1 and upper frequency ν2) both for Atoll and Z sources. For the data without shift-and-add, we find that Atoll and Z sources show different distributions of ν1, ν2 and ν2/ ν1, but the same distribution of Δ ν (difference of twin kHz QPOs), which indicates that twin kHz QPOs may share the common properties of LXMBs and have the same physical origins. The distribution of Δ ν is quite different from a constant value, so is ν 2/ ν1 from a constant ratio. The weighted mean values and maxima of ν1 and ν2 in Atoll sources are slightly higher than those in Z sources. We also find that shift-and-add technique can reconstruct the distributions of ν1 and Δ ν. The K-S test results of ν1 and Δ ν between Atoll and Z sources from data with shift-and-add are quite different from those without it, and we think that this may be caused by the selection biases of the sample. We also study the properties of the quality factor ( Q) and the root-meansquared (rms) amplitude of 4U 0614+09 with data from the two observational methods, but the errors are too big to make a robust conclusion. The NS spin frequency ( ν s) distribution of 28 NS-LMXBs show a bigger mean value (∼408 Hz) than that (∼281 Hz) of the radio binary millisecond pulsars (MSPs), which may be due to the lack of the spin detections from Z sources (systematically lower than 281 Hz). Furthermore, on the relations between the kHz QPOs and NS spin frequency ν s, we find the approximate correlations of the mean values of Δ ν with NS spin and its half, respectively. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
- Subjects
PLASMA oscillations; NEUTRON stars; X-ray binaries; STANDARD deviations; QUALITY factor; PULSAR detection
- Publication
Astronomische Nachrichten, 2014, Vol 335, Issue 2, p168
- ISSN
0004-6337
- Publication type
Article
- DOI
10.1002/asna.201311995