X-ray timing analysis of the quasar PG 1211+143

TL;DR

This study presents a detailed X-ray timing analysis of quasar PG 1211+143, revealing characteristic variability patterns, a bend in the power spectrum consistent with black hole scaling relations, and multi-timescale UV variability.

Contribution

It provides new insights into the timing properties and variability behavior of PG 1211+143, including the detection of a power spectrum bend and energy-dependent rms, using extensive X-ray and UV observations.

Findings

Detection of a power spectrum bend at ~7e-5 Hz.

Confirmation of the rms-flux relation in the quasar.

Observation of UV variability on days to weeks timescales.

Abstract

We report on a timing analysis of a new ~630ks XMM-Newton observation of the quasar, PG 1211+143. We find a well-defined X-ray power spectrum with a well-detected bend at ~7e-5 Hz, consistent with the established bend-timescale--black-hole-mass correlation for luminous, accreting black holes. We find the linear rms-flux relation commonly observed in accreting black hole systems and investigate the energy-dependence of the rms. The fractional rms is roughly constant with energy on short timescales (< 1 day; within observations) whereas there is enhanced soft band variability on long timescales (between observations typically spaced by a few days). Additionally, we also report on the optical--UV variability using the OM on-board XMM-Newton and a ~2-month-long overlapping monitoring programme with Swift. We find that, although there is little UV variability within observations (<1 day), UV variations of a few per cent exist on time-scales of ~days--weeks.