Timing analysis of J0054. Left panel: Fourier power spectrum of the Chandra data of J0054. The red line indicates the local 3.5σ detection threshold adopted in the CAT at BAR project. The prominent peak well above the threshold (5.9σ) corresponds to the ∼6 h modulation of J0054. The inset shows the pulse profile obtained by folding the data at the best period of 5.88 ± 0.12 h. Right panel: light curve (the background is negligible). The bin time is 2500 s.