Table 1.
kHz QPOs and neutron star spin of 4U 1728-34 and the inferred parameters.
| Interval | ν1a | ν2b | νsc | rd | B(r)e | rcof |
|---|---|---|---|---|---|---|
| number | (Hz) | (Hz) | (Hz) | (km) | (G) | (km) |
| [1] …… | … | 387 ± 18 | 363 | 33.0 | 4.8 × 106 | 34.4 |
| [2] …… | … | 397 ± 14 | 32.4 | 5.1 × 106 | ||
| [3] …… | … | 466 ± 21 | 29.1 | 7.0 × 106 | ||
| [4] …… | … | 497.8 ± 5.3 | 27.9 | 8.0 × 106 | ||
| [5] …… | … | 498.7 ± 5.9 | 27.9 | 8.0 × 106 | ||
| [6] …… | … | 517.3 ± 8.1 | 27.2 | 8.6 × 106 | ||
| [7] …… | … | 694.5 ± 9.3 | 22.3 | 1.5 × 107 | ||
| [8] …… | … | 729.0 ± 3.5 | 21.6 | 1.7 × 107 | ||
| [9] …… | … | 789.6 ± 2.5 | 20.5 | 2.0 × 107 | ||
| [10] …… | 511 ± 17 | 846.9 ± 2.0 | 19.6 | 2.3 × 107 | ||
| [11] …… | 559 ± 11 | 872.9 ± 1.6 | 19.2 | 2.4 × 107 | ||
| [12] …… | 599 ± 14 | 905.2 ± 2.6 | 18.7 | 2.6 × 107 | ||
| [13] …… | 673 ± 10 | 948.8 ± 3.8 | 18.1 | 2.9 × 107 | ||
| [14] …… | 750.9 ± 3.7 | 1054.7 ± 8.7 | 16.9 | 3.6 × 107 | ||
| [15] …… | 773.0 ± 1.8 | 1105.8 ± 6.8 | 16.4 | 3.9 × 107 | ||
| [16] …… | 816.0 ± 4.0 | 1129 ± 13 | 16.2 | 4.1 × 107 | ||
| [17] …… | 876.1 ± 2.6 | 1158 ± 18 | 15.9 | 4.3 × 107 |
Notes.
ν1 – Frequency of the lower kHz QPO from Di Salvo et al. (2001).
ν2 – Frequency of the upper kHz QPO from Di Salvo et al. (2001).
νs – Frequency of the neutron star spin from Strohmayer et al. (1996).
r – Emission radius of the kHz QPOs (the magnetosphere-disk radius) inferred by Eq. (2) with the assumed NS mass M ∼ 1.6 M⊙.
B(r) – Magnetic field strength at the magnetosphere-disk radius inferred by Eq. (3) with the assumed NS surface magnetic field strength Bs ∼ 108 G and NS radius R ∼ 12 km.
rco – Corotation radius inferred by Eq. (4) with the assumed NS mass M ∼ 1.6 M⊙.
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