Scientists have made the most detailed observation till date of a black hole outflow from the active galaxy IRAS 13224-3809. The outflow's temperature changed on time scales of less than an hour -- hundreds of times faster than ever seen before. The rapid fluctuations in the outflow's temperature also indicated that the outflow was responding to X-ray emissions from the accretion disk.
Gas outflows are common features of active supermassive black holes that reside in the center of large galaxies. Millions to billions of times the mass of the Sun, these black holes feed on large disks of gases that swirl around them. Occasionally the black holes eat too much and burp out an ultra-fast wind called an outflow.
The new observations are published in the journal Nature dated March 2, 2017.
Scientists made these measurements using two space telescopes, NASA's NuSTAR (Nuclear Spectroscopic Telescope Array) telescope and the European Space Agency's (ESA) XMM-Newton.
To measure the temperatures of these winds, scientists studied X-rays coming from the edge of the black hole. As they travel towards Earth, these X-rays pass through the outflows. Elements such as iron or magnesium present in the outflows can absorb specific parts of the X-ray spectrum, creating signature "dips" in the X-ray signal. By observing these dips, called absorption features, astronomers can learn what elements exist in the wind.
The team noticed that the absorption features disappeared and reappeared in the span of a few hours. The researchers concluded that the X-rays were heating up the winds to millions of degrees Celsius, making the winds incapable of absorbing any more X-rays.
“All that information will be crucial to understanding how these outflows are connected to galaxy formation”, said Erin Kara, a postdoctoral researcher in astronomy at the University of Maryland.