Long XMM observation of the Narrow-Line Seyfert 1 galaxy IRAS13224-3809: rapid variability, high spin and a soft lag

TL;DR

This study presents a detailed 500ks XMM-Newton observation of IRAS13224-3809, revealing rapid variability, a high black hole spin of 0.988, and a soft X-ray lag, supporting models of reflection from an inner accretion disk around a rapidly spinning black hole.

Contribution

First precise measurement of black hole spin and inner disk reflection features in IRAS13224-3809 using long XMM-Newton data.

Findings

Black hole spin measured at 0.988 with high precision

Detection of a 100s soft X-ray lag

Rapid variability on timescales of a few hundred seconds

Abstract

Results are presented from a 500ks long XMM-Newton observation of the Narrow-Line Seyfert 1 galaxy IRAS13224-3809. The source is rapidly variable on timescales down to a few 100s. The spectrum shows strong broad Fe-K and L emission features which are interpreted as arising from reflection from the inner parts of an accretion disc around a rapidly spinning black hole. Assuming a power-law emissivity for the reflected flux and that the innermost radius corresponds to the innermost stable circular orbit, the black hole spin is measured to be 0.988 with a statistical precision better than one per cent. Systematic uncertainties are discussed. A soft X-ray lag of 100s confirms this scenario. The bulk of the power-law continuum source is located at a radius of 2-3 gravitational radii.