X-ray time lags in PG 1211+143

TL;DR

This study analyzes X-ray time lags in PG 1211+143, revealing both hard and soft lag behaviors across different frequencies, with implications for accretion processes and variability modes.

Contribution

It provides the first detection of a hard lag in PG 1211+143 and explores the energy dependence and complexity of lag behavior over various timescales.

Findings

Detection of a hard lag up to ~3ks at low frequencies.

Energy dependence of the lag scales with log(E).

Presence of a high-frequency soft lag peaking at <0.8ks.

Abstract

We investigate the X-ray time lags of a recent ~630ks XMM-Newton observation of PG 1211+143. We find well-correlated variations across the XMM-Newton EPIC bandpass, with the first detection of a hard lag in this source with a mean time delay of up to ~3ks at the lowest frequencies. We find that the energy-dependence of the low-frequency hard lag scales approximately linearly with log(E) when averaged over all orbits, consistent with the propagating fluctuations model. However, we find that the low-frequency lag behaviour becomes more complex on timescales longer than a single orbit, suggestive of additional modes of variability. We also detect a high-frequency soft lag at ~10^{-4}Hz with the magnitude of the delay peaking at <0.8ks, consistent with previous observations, which we discuss in terms of small-scale reverberation.