Researchers measure temperature swings of black hole winds

In a first, scientists have measured rapidly varying temperatures in hot gas emanating from around a black hole and found that the winds can heat up and cool down in the span of just a few hours.

The findings, published in the journal Nature, could shed new light on how winds emanating from around a black hole can affect the environment of host galaxies.

For the study, the researchers used data from NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) telescope and the European Space Agency's XMM-Newton telescope.

"We know that supermassive black holes affect the environment of their host galaxies, and powerful winds arising from near the black hole may be one means for them to do so," said NuSTAR Principal Investigator Fiona Harrison, Professor at California Institute of Technology in the US.

"The rapid variability, observed for the first time, is providing clues as to how these winds form and how much energy they may carry out into the galaxy," Harrison said.

The black hole that the researchers observed is located in the active galaxy IRAS 13224-3809 in the constellation Centaurus.

To measure the temperatures of these winds created by disks of matter surrounding black holes, the team studied X-rays coming from the edge of the black hole.

As they travel toward Earth, these X-rays pass through the winds, and some wavelengths of the X-ray spectrum are absorbed by different elements in the winds, such as iron and magnesium.

By examining the holes, or "absorption features", in the X-ray spectrum as it reaches Earth, astronomers can learn more about the components of the wind.

While observing this spectrum, the team noticed that the absorption features were disappearing and reappearing in the span of a few hours.

The team concluded that the X-rays were actually heating up the winds to very high temperatures so that they became incapable of absorbing any more X-rays.

The winds then cool off, and the absorption features return, starting the cycle over again.

"This is the first time we have seen that winds are interacting with the black hole's radiation," study first author Michael Parker, postdoctoral scholar at University of Cambridge Institute of Astronomy in Britain

--IANS

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