Results of the Z² search (EPIC-pn data, P = 0.1468−54 000 s). The frequency range is Δν ~ 6.8 Hz, the energy band is 0.2 − 7 keV and the size of the extraction region is 10″, amounting to ~13 500 counts. Dashed horizontal lines show confidence levels of 1σ to 4σ for the detection of a periodic signal, given the frequency range, the duration of the observation and the number of source photons in the search. For plotting purposes, a logarithmic step in frequency was adopted, resulting in a smaller number of frequency trials than in the original search (of the order of 3.4 × 10⁶ data points). No significant periodicity with pulsed fraction higher than ~5% (1σ) is found.