2005A&A...437..209B


Query : 2005A&A...437..209B

2005A&A...437..209B - Astronomy and Astrophysics, volume 437, 209-216 (2005/7-1)

The distribution of kHz QPO frequencies in bright low mass X-ray binaries.

BELLONI T., MENDEZ M. and HOMAN J.

Abstract (from CDS):

We analyzed all published frequencies, ν1 and ν2, of the twin kilohertz quasi-periodic oscillations (kHz QPOs) in bright neutron star low-mass X-ray binaries. The two frequencies are well correlated but, contrary to recent suggestions, the frequency-frequency correlation is significantly different from a ν2=(3/2)ν1 relation. To check whether, although not following the the 3/2 relation, the QPO frequencies cluster around a region where ν21≃3/2, we re-analyzed the Sco X-1 data that were used to report that ratio and show that, because the distribution of ratios of linearly correlated measurements is intrinsically biased, although the significance of the clustering around ν21≃3/2 previously reported in the case of Sco X-1 is formally correct, it does not provide any useful information about a possible underlying resonance mechanism in this source. Using the same data, we then show that the (unbiased) distribution of QPO frequencies is consistent with a uniform distribution at a 2.4σ level. To investigate this further, we analyzed a larger data set of Sco X-1 and four other sources, 4U 1608-52, 4U 1636-53, 4U 1728-34 and 4U 1820-30. We find that for all five sources the distribution of the kHz QPO frequencies is not uniform and has multiple peaks, which have no analogy in the distribution of points in the spectral color-color diagrams of these sources. Finally, we demonstrate that a simple random walk of the QPO frequencies can reproduce qualitatively the observed distributions in frequency and frequency ratio. This result weakens the support for resonance models of kHz QPOs in neutron stars.

Abstract Copyright:

Journal keyword(s): accretion, accretion disks - stars: neutron - binaries: close - X-rays: binaries

Simbad objects: 15

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Number of rows : 15
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 V* V1055 Ori LXB 06 17 07.3 +09 08 13   18.80 18.5     ~ 539 1
2 V* QX Nor LXB 16 12 43.0 -52 25 23           ~ 869 1
3 V* V818 Sco LXB 16 19 55.0692669024 -15 38 25.017666540 11.60 12.40 11.1     Oev 1570 0
4 V* V801 Ara LXB 16 40 55.5976953528 -53 45 04.948107156 17.50 18.20 17.5   17.07 ~ 822 1
5 4U 1642-45 LXB 16 45 47.7 -45 36 40     14.30     ~ 392 1
6 4U 1705-44 LXB 17 08 54.470 -44 06 07.35           ~ 370 0
7 NAME Slow Burster LXB 17 31 57.73 -33 50 02.5     15.50     ~ 792 1
8 KS 1731-260 LXB 17 34 13.46 -26 05 18.6       22.8 20.9 ~ 404 0
9 V* V926 Sco LXB 17 38 58.3 -44 27 00 16.90 17.70 17.5     ~ 441 0
10 4U 1758-25 LXB 18 01 09.7308060816 -25 04 44.120221284     11.08     ~ 628 1
11 V* NP Ser LXB 18 16 01.389 -14 02 10.62   18.8       K 616 2
12 X Sgr X-4 LXB 18 23 40.57 -30 21 40.6   19.06 18.81     ~ 947 1
13 V* V1405 Aql LXB 19 18 47.871 -05 14 17.09 20.90 21.40 21.0     ~ 456 0
14 V* LZ Aqr LXB 21 23 14.54 -05 47 52.9 15.90 16.78 16.8     ~ 144 0
15 V* V1341 Cyg LXB 21 44 41.1544345272 +38 19 17.066570988 15.00 15.13 14.68 15.00   A9III 1104 1

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2022.05.22-14:27:48

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