Ultra-fast winds and temperature swings measured around a supermassive black hole

Artist's concept of a supermassive black hole with ultrafast winds (Image ESA)
Artist’s concept of a supermassive black hole with ultrafast winds (Image ESA)

An article published in the journal “Nature” describes the most detailed observations of incredibly fast winds that travel at speeds of up to 71,000 km/s, nearly a quarter of the speed of light, near a supermassive black hole. A team of researchers used NASA’s NuSTAR and ESA’s XMM-Newton space telescopes to observe this phenomenon at the center of the galaxy IRAS 13224-3809 recording very quick temperature changes.

IRAS 13224-3809 is a galaxy with an active nucleus. The X-rays emitted by the supermassive black hole that powers the active nucleus are a consequence of the gas accretion process and come from the innermost areas, relatively close to the black hole. The connections between this process and the ultrafast winds are still poorly understood and this research, which detected for the first time the interaction between the winds and the X-rays, provided new information about them.

This research is based on a real campaign of observations with specific instruments for X-ray astronomy when the XMM-Newton space telescope was aimed at the supermassive black hole for 17 consecutive days while NuSTAR, launched in June 2012, observed it for six days.

These observations allowed to detect the extreme variability of the winds with changes occurring in a few hours that are normally observed in months in an active galactic nucleus. It’s a young energetic black hole so it swallows gas so quickly that it causes powerful jets of gas and ultrafast winds carrying huge amounts of materials.

The temperature and relative changes were measured by studying the X-rays coming from the edges of the supermassive black hole. These X-rays pass through the ultrafast winds and are influenced with the absorption of certain wavelengths caused by the presence of certain elements such as iron and magnesium. The study of the X-ray wavelengths spectrum allows to better understand the winds’s components.

During this study, the researchers realized that the changes occured in a matter of hours. Their conclusion was that the X-rays warmed the winds up to temperatures of millions of degrees up to the point where they couldn’t absorb them any more. At that point, the winds cooled down and the X-ray absorption resumed, starting the cycle again.

The changes detected also affect the chemical characteristics of the jets of gas due to the X-ray emissions that ionize the atoms, stripping their electrons. Again the changes turned out to be very quick, hundreds of times faster than previous observations of phenomena of this type.

The high variability of the supermassive black hole in the galaxy IRAS 13224-3809 and the evidence found of the link with the X-ray emissions are already helping to better understand the mechanisms of the winds coming from the black hole. These active galactic nuclei have a strong influence on the galaxies that host them, so much that they can also limit the birth of new stars. That means that their study is important to better understand galaxy evolution as well.

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