1H0707-495 in 2011: An X-ray source within a gravitational radius of the event horizon

TL;DR

This study analyzes the 2011 low state of galaxy 1H0707-495, revealing a highly concentrated X-ray emission near the black hole's event horizon, suggesting a rapidly spinning black hole with the source within one gravitational radius.

Contribution

It provides evidence that the X-ray source is located within one gravitational radius of the black hole's event horizon, indicating a very close proximity of the emission region to the black hole.

Findings

The source's spectrum in 2011 shows a sharp drop extending below 6 keV.

The emission is concentrated to the central part of the accretion disc.

The irradiating source lies within 1 gravitational radius of the black hole.

Abstract

The Narrow Line Seyfert 1 Galaxy 1H0707-495 went in to a low state from 2010 December to 2011 February, discovered by a monitoring campaign using the X-Ray Telescope on the Swift satellite. We triggered a 100 ks XMM-Newton observation of the source in 2011 January, revealing the source to have dropped by a factor of ten in the soft band, below 1 keV, and a factor of 2 at 5 keV, compared with a long observation in 2008. The sharp spectral drop in the source usually seen around 7 keV now extends to lower energies, below 6 keV in our frame. The 2011 spectrum is well fit by a relativistically-blurred reflection spectrum similar to that which fits the 2008 data, except that the emission is now concentrated solely to the central part of the accretion disc. The irradiating source must lie within 1 gravitational radius of the event horizon of the black hole, which spins rapidly. Alternative models are briefly considered but none has any simple physical interpretation.