PG 1211+143: probing high-frequency lags in a high-mass active galactic nucleus

Abstract

We present the timing analysis of the four archived XMM-Newton observations of PG 1211+143. The source is well-known for its spectral complexity, comprising a strong soft excess and different absorption systems. Soft energy band (0.3-0.7 keV) lags are detected over all the four observations, in the frequency range ν≲ 6 × 10^-4 Hz, where hard lags, similar to those observed in black hole X-ray binaries, are usually detected in smaller mass active galactic nuclei (AGN). The lag magnitude is energy-dependent, showing two distinct trends apparently connectable to the two flux levels at which the source is observed. The results are discussed in the context of disc- and/or corona-reprocessing scenarios, and of disc wind models. Similarities with the high-frequency negative lag of 1H 0707-495 are highlighted, and, if confirmed, they would support the hypothesis that the lag in PG 1211+143 represents the signature of the same underlying mechanism, whose temporal characteristics scale with the mass of the central object.