Light bending and X-ray echoes from behind a supermassive black hole

TL;DR

This study observes X-ray echoes and light bending around a supermassive black hole in galaxy I Zw 1, confirming predictions of General Relativity through detection of photons reverberating from behind the black hole.

Contribution

It provides new observational evidence of photons bent around a black hole, revealing the environment behind the event horizon and supporting relativistic models.

Findings

Detection of relativistically broadened iron K line and Compton hump.

Observation of photons reverberating from behind the black hole.

Confirmation of light bending predicted by General Relativity.

Abstract

The innermost regions of accretion disks around black holes are strongly irradiated by X-rays that are emitted from a highly variable, compact corona, in the immediate vicinity of the black hole. The X-rays that are seen reflected from the disk and the time delays, as variations in the X-ray emission echo or reverberate off the disk provide a view of the environment just outside the event horizon. I Zwicky 1 (I Zw 1), is a nearby narrow line Seyfert 1 galaxy. Previous studies of the reverberation of X-rays from its accretion disk revealed that the corona is composed of two components; an extended, slowly varying component over the surface of the inner accretion disk, and a collimated core, with luminosity fluctuations propagating upwards from its base, which dominates the more rapid variability. Here we report observations of X-ray flares emitted from around the supermassive black hole in I Zw 1. X-ray reflection from the accretion disk is detected through a relativistically broadened iron K line and Compton hump in the X-ray emission spectrum. Analysis of the X-ray flares reveals short flashes of photons consistent with the re-emergence of emission from behind the black hole. The energy shifts of these photons identify their origins from different parts of the disk. These are photons that reverberate off the far side of the disk and bent around the black hole and magnified by the strong gravitational field. Observing photons bent around the black hole confirms a key prediction of General Relativity.