Quick radio splashes: key to unraveled secrets

In 2007, one of the most mysterious phenomena in modern astrophysicics was discovered: fast radio -bar (Fast Radio Bursts, FRB). The first of them was found in the archival data of the Parks radio telescope (Australia) - a millisecond surge in high -intensity radio radiation, which had a very strong dependence of the frequency signal delay. This dependence is called a measure of dispersion, it occurs with the spread of a radio signal in the cosmic interstellar and intergalactic plasma and is proportional to the density of the electronic component, which is interpreted along the beam of vision.

The author of the discovery Duncan Lorimer suggested that, most likely, the source was an illegal object, at a distance of about hundred Megaparsecs. A few years later, radio -autoons opened similar bursts with similar properties, and it became clear that this was a whole class of new astronomical phenomena. Now they are known about 20, and statistical analysis shows that the number of fast radio splashes per day throughout the sky should be about several thousand!

But the question remained - where do they come from? Where are the sources nearby in the galaxy, in neighboring galaxies or even at cosmological distances in billions of light years? The accuracy of the localization of fast radio splashes in the sky was still small - several square degrees. Searching a source on such an area, besides not knowing what he should be like, is a hopeless task.

What is their uniqueness? A short duration and high intensity indicate a colossal bright radiation temperature in the source. This kind of radio emission was known only from the ultra -short "superimpuls" of young pulsars (for example, crab), the nature of which is also unclear. Currently, hundreds of articles have been written about the nature of short radio supports (FRB) and several dozen hypotheses have been put forward from completely natural (for example, connecting them with explosive processes near neutron stars, Arxiv: 1307.4924, Arxiv: 1401.6674) to quite exotic (for example, explosive decay of “axionic mini-clusteers”,, of the explosive decay ARXIV: 1411.3900) or even (for now) fantastic (for example, radiois used by extraterrestrial civilizations for the dispersal of “space sails” for movement in the interplanetary and interstellar space, ARXIV: 1701.01109).

The situation with fast radio splashes is very reminiscent of the story with gamma-varnishes for almost half a century. Then, too, they could not find sources due to poor localization, they also did not know the scale of the distance to them. In the early 1990s, the point of view dominated that the sources are in the galaxy. But their statistics, recruited by the Gamma Observatorium, said that gamma-implains come from cosmological distances comparable to the distance to the horizon of the Universe.

On this occasion, the library of the US Congress in 1995 took place exciting public debate between Donald Q. Lamb), adhering to the galactic hypothesis, and Bogdan Paczynski, which defended the cosmological origin of the gamma-vplesov. Then no one won a clear victory, but in 1996 the riddle was resolved. They found an optical echoing surge, which coincided with a distant galaxy with a large red displacement. Then more and more - everything is at cosmological distances. The key to clue was the determination of the coordinates of the source with astrometric accuracy.

Astrometry is the most accurate area of ​​astronomy; The definition of coordinates of heavenly objects and their visible movements is one of its main tasks. The most accurately coordinates are determined using interferometry, especially in the radiodiapas, where the base can be comparable with the size of the Earth, and in space experiments (“radio -Astro”) - even ten times more.

For a long time it remained a problem to catch a radio capeus using an interferometer due to a narrow field of vision. And on January 4, 2017, in the journal Nature , a large group of radio-astronomers (S. Chatterjee et al., Arxiv: 1701.01098), finally reported “astrometric” localization of one of the short pulses of FRB 121102 using radio interferometric observations on VLA antennas and 305-meter radio teleshop In Aresibo (USA).

Astronomers took advantage of the fact that this particular source is repeated-for 83 hours of observation at VLA in a frequency band 2.5-3.5 GHz for six months from it, 9 short bright bursts with the same measure of dispersion were registered. The accuracy of localization was about 0.1 angular seconds (this is the accuracy of the best optical observations).

It turned out that next to the source of repeated FRB (at a distance of 0.1 seconds of the arc) there is a weak almost permanent radio source with a continuous nettle spectrum. According to archival data from the observations of 2014, on the optical 10-meter telescope KEK and the Dzhemini telescope, about 25 stellar objects were revealed at the source of the source.

Additional radio interferometric observations with a super -dune base (VLBI) on the network of European radio telescopes with millisecond accuracy confirmed the results of VLA (ARXIV: 1701.01099) and showed that the constant source and source of FRB are divided into less than 0.12 milliseconds of arcs. This confirms their possible physical connection.

Spectroscopy of the optical source on the telescope "North Dzhemini" (Hawaii) showed (Arxiv: 1701.01100), which optical radiation is a weak dwarf galaxy with a red displacement Z = 0.1927 (distance about 1 GPK), with a mass of 40-70 million masses, with a high unit pace of star formation and a low stars Metal personality, similar to young dwarf galaxies with a flash of star formation.

What are the conclusions from these discoveries? Firstly, the non-Halactic nature (at least this!) FRB source is confirmed. Secondly, a permanent second radio source with a non -dimensional spectrum has been found, which has not yet been identified with well -known sources (for example, a young neutron star -a mugnetar or with the core of an active galaxy). Thirdly, the source is precisely in the dwarf galaxy with low metal and a high pace of star formation.

Obviously, these facts confidently reject a number of physical models, but still do not allow to unequivocally answer the question of the nature of FRB and their unusual radio radiation. Presumably, in the near future, new observations will allow astronomers to solve the secret of the sources of short radio supports - we are waiting for new results!

Konstantin Zvennov,
doct. physical. sciences, professor of the Department of Astrophysics and Star
astronomy of the astronomical department of the Faculty of Physics of Moscow State University