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Table 2

Power-law slopes β and γ describing the cumulative luminosity distribution (see Sects. 2.3.1 and 2.3.2) for the known UCXB population based on the RXTE ASM data.

Name Porb  (min) β γ

4U 1820–30 11.42  −7.4  −3.7
4U 0513–40 17  −2.0  −2.3
2S 0918–549 17.4  −1.03  −2.5
4U 1543–624 18.2  −3.8  −4.3
4U 1850–087 20.6  −1.9  −2.1
M 15 X-2 22.58  −1.6  −3.0
XTE J1807–294 40.07  −2.4 N/A
4U 1626–67 41.4  −3.0  −2.5
XTE J1751–305 42.42  −2.5  −0.55
XTE J0929–314 43.58  −2.8 N/A
4U 1916–05 49.48  −2.8  −2.5
SWIFT J1756.9–2508 54.70  −1.3  −1.7

4U 1728–34 10.77?  −6.3  −0.66
4U 0614+091 51.3?  −3.2  −4.1

Notes. The two systems below the line are UCXB candidates, with an uncertain orbital period. If no γ-value is given, the source is too faint on average for this method to work.

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