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We have analysed the new  Rossi X‐ray Timing Explorer  Proportional Counter Array data of the atoll neutron star (NS) low‐mass X‐ray binary (LMXB) system XB  1254− 690. The colour–colour diagram shows that the source was in the high‐intensity banana state. We have found two low‐frequency candidate peaks with single trial significances of  ≈2.65 × 10 −8   and  ≈7.39 × 10 −8   in the power spectra. After taking into account the number of trials, the joint probability of appearance of these two peaks in the data set only by chance is  ∼ 4.5 × 10 −4  , and hence a low‐frequency quasi‐periodic oscillation can be considered to be detected with a significance of  ∼ 4.5 × 10 −4  , or  ∼ 3.5σ  for the first time from this source. We have also done the first systematic X‐ray spectral study of XB  1254− 690, and found that, while one‐component models are inadequate, three‐component models are not required by the data. We have concluded that a combined broken‐power‐law and Comptonization model best describes the source continuum spectrum among 19 two‐component models. The plasma temperature (∼3 keV) and the optical depth (∼7) of the Comptonization component are consistent with the previously reported values for other sources. However, the use of a broken‐power‐law component to describe the NS LMXB spectra has recently been started, and we have used this component for XB  1254− 690 for the first time. We have attempted to determine the relative energy budgets of the accretion disc and the boundary layer using the best‐fitting spectral model, and concluded that a reliable estimation of these budgets requires correlations among time variations of spectral properties in different wavelengths.

Timing and spectral study of XB 1254−690 using new RXTE PCA data