The nature of the extreme X-ray variability in the NLS1 1H 0707-495

TL;DR

This study analyzes X-ray data of the NLS1 galaxy 1H 0707-495, revealing that its extreme variability results from a combination of intrinsic activity and environmental absorption, especially during obscuration events.

Contribution

It provides a detailed spectral and temporal analysis of variability origins in 1H 0707-495, highlighting the roles of absorption and emission processes in extreme X-ray variability.

Findings

Extreme soft variability linked to obscuration and emission suppression.

Long-term variability driven by absorption changes.

High-frequency variability is intrinsic to the source.

Abstract

We examine archival XMM-Newton data on the extremely variable narrow-line Seyfert 1 (NLS1) active galactic nucleus (AGN) 1H 0707-495. We construct fractional excess variance (Fvar) spectra for each epoch, including the recent 2019 observation taken simultaneously with eROSITA. We explore both intrinsic and environmental absorption origins for the variability in different epochs, and examine the effect of the photoionised emission lines from outflowing gas. In particular, we show that the unusual soft variability first detected by eROSITA in 2019 is due to a combination of an obscuration event and strong suppression of the variance at 1 keV by photoionised emission, which makes the variance below 1 keV appear more extreme. We also examine the variability on long timescales, between observations, and find that it is well described by a combination of intrinsic variability and absorption variability. We suggest that the typical extreme high frequency variability which 1H 0707-495 is known for is intrinsic to the source, but the large amplitude, low frequency variability that causes prolonged low-flux intervals is likely dominated by variable low-ionisation, low velocity absorption.