X-ray reverberation in NLS1

TL;DR

This paper presents evidence of X-ray reverberation in NLS1 galaxies, indicating scattering material near the black hole, and refutes alternative models suggesting delays occur very close to the event horizon.

Contribution

It provides the first clear detection of X-ray reverberation signatures in NLS1 galaxies, confirming the presence of scattering material at tens to hundreds of gravitational radii.

Findings

Detection of characteristic time-delay signatures in NLS1s

Evidence for high covering fraction of scattering material

Refutation of models placing delays at one gravitational radius

Abstract

Reverberation from scattering material around the black hole in active galactic nuclei is expected to produce a characteristic signature in a Fourier analysis of the time delays between directly-viewed continuum emission and the scattered light. Narrow-line Seyfert 1 galaxies (NLS1) are highly variable at X-ray energies, and are ideal candidates for the detection of X-ray reverberation. We show new analysis of a small sample of NLS1 that clearly shows the expected time-delay signature, providing strong evidence for the existence of a high covering fraction of scattering and absorbing material a few tens to hundreds of gravitational radii from the black hole. We also show that an alternative interpretation of time delays in the NLS1 1H0707-495, as arising about one gravitational radius from the black hole, is strongly disfavoured in an analysis of the energy-dependence of the time delays.