Millihertz quasi-periodic oscillations and broad iron line from LMC X-1

We study the temporal and energy spectral characteristics of the persistent black hole Xray LMC X-1 using two XMM–Newton and a Suzaku observation. We report the of low-frequency (∼26–29 m Hz) quasi-periodic oscillations (QPOs). We also report variability of the broad iron Kα line studied earlier with Suzaku. The QPOs are found to be with fractional rms amplitude in the ∼1–2 per cent range and quality factor Q ∼ 2–10. are accompanied by weak red noise or zero-centred Lorentzian components with rms at the ∼1–3 per cent level. The energy spectra consist of three varying components – disc blackbody (kTin ∼ 0.7–0.9 keV), high-energy power-law tail ( ∼ 2.4–3.3) a broad iron line at 6.4–6.9 keV. The broad iron line, the QPO and the strong power-law are not always present. The QPOs and the broad iron line appear to be clearly in the presence of a strong power-law component. The broad iron line is found to be when the disc is likely truncated and absent when the power-law component almost . These results suggest that the QPO and the broad iron line together can be used to the dynamics of the accretion disc and the corona. words: accretion, accretion discs – black hole physics – binaries: spectroscopic – stars: