The "hiccup" in the center of a distant galaxy, observed in 2020, was explained by the rotation of a small black hole that punches holes in the accretion disk. For the first time, scientists have found a system of supermassive and ordinary black holes.
Illustration of a pair of supermassive and small black holes. Flying around the "older" sister, a small hole pierces the accretion disk, provoking regular changes in brightness. However, scientists noticed them only because of the increased brightness of the disk / © Jose-Luis Olivares, MIT
The first confirmed gravitational waves caught by the LIGO observatory in 2015 came from the merger of two black holes, scientists believe. Over the past years, astronomers have recorded gravitational waves from dozens of such events. Moreover, these are almost always "dark" events, when black holes of moderate masses merge without significant luminescence.
In order to observe mergers well, other events are needed – for example, involving large black holes with an accretion disk visible in telescopes. And in general, it would be good to start observing such events in advance, so astronomers are looking for suitable pairs of cosmic bodies. One of the most promising combinations is a compact object next to a supermassive black hole. Researchers found this object by chance.
In 2020, the ASAS-SN automated telescope network, which scans the sky daily for supernovae and other short-lived events, caught the flare. The galaxy 800 million light-years from us has become a thousand times brighter. Noticing the event notification, Dheeraj Pasham (Dheeraj Pasham), an astrophysicist from the Massachusetts Institute of Technology (USA), directed the NASA NICER X-ray telescope installed on the ISS to the galaxy. For about four months, the telescope regularly took pictures of the object. Other observatories also participated in data collection.
After analyzing the collected data and conducting a statistical analysis, a group of scientists led by Pasham came to the conclusion that matter escapes from the accretion disk of a supermassive black hole every 8.5 days, suppressing the radiation for a short time. In some ways, it was similar to the variations in the radiation of a star next to which a planet flies.
Why did astronomers not notice this "hiccup" before? Because the accretion disk was quite dim. Apparently, a star flew too close to a supermassive black hole and was torn apart. This tidal destruction event triggered a burst in the brightness of the disk, which was detected by telescopes. While studying the surge, scientists noticed a periodicity.
The authors of the study considered various hypotheses for the occurrence of "flickering", using, in particular, two-dimensional computer simulations: features of the accretion disk, the destruction of the star in parts, the flow of debris from the destroyed star, and others. Thus, the researchers came to the conclusion that the culprit is a compact object that rotates around a supermassive black hole at a great inclination. The results are published in the journal Science Advances.
It should be an object with a mass of 100 to 10,000 solar masses, that is, a medium-mass black hole. Although such a pair was discovered for the first time, according to the authors of the new paper, within 800 million light years from us, among 2.5 million galaxies, up to five (from 0.07 to 5.3, to be more precise) events can occur per year tidal destruction in just such galaxies - with a pair of supermassive and ordinary black holes. This, of course, is not enough, but during long-term observation of the active nuclei of galaxies, it is quite possible to catch a "hiccup" during the absorption of another star and, according to its periodicity, "see" a compact but massive companion.
It turns out that the accretion disks of supermassive black holes are not so "smooth". Black holes and probably stars can fly in them.
No comments:
Post a Comment