ESA’s XMM-Newton X-ray observatory has used, for the first time, the reverberating echoes of X-ray radiation in order to map the dynamic behaviour and surroundings of a black hole (BH). This emission is the result of the infalling material into a BH. Specifically, as the material falls into the BH, it is heated up and emits X-ray radiation. These regions are highly distorted due to the extreme conditions of the environment and the strong gravity of the BH. Even if it is hard to resolve the environment of the BHs, we can investigate the behaviour of these peculiar objects, indirectly, by observing the infalling material. Based on the properties of this matter, a group of Astrophysicists, determine the mass and spin of IRAS 13224–3809 central BH. This galaxy is one of the most variable X-ray sources in the sky undergoing significant and rapid variation in brightness. To carry out this work, the group, used the longest observation of an accreting BH ever taken with XMM-Newton (2 million seconds). While the scientific team expected to observe the reverberation echoes, they noticed that the “corona” – a region of very hot electrons located above the BH – changed in size extremely fast.
William Alston, lead author of the relevant study, explains: “As the corona’s size changes, so does the light echo – a bit like if the cathedral ceiling is moving up and down, changing how the echo of your voice sounds. By tracking the light echoes, we were able to track this changing corona, and – what’s even more exciting – get much better values for the black hole’s mass and spin than we could have determined if the corona was not changing in size. We know the black hole’s mass cannot be fluctuating, so any changes in the echo must be down to the gaseous environment”.
Relevant paper: “A dynamic black hole corona in an active galaxy through X-ray reverberation mapping” by W. N. Alston et al. is published in the journal Nature Astronomy.
(Picture: An artist’s impression of XMM-Newton – ESA)