New about quick radio

At the end of February, important astronomical news appeared: for the first time it was possible to determine the birthplace of the so -called quick radio splashes. The FRB 150418 event itself (as follows from its designation) was observed in April last year. The place of its appearance has been announced an elliptical galaxy, remote from us for 6 billion light years, which would seem to exclude the theory about the generation of radio surges with relatively low -power magnets in our galaxy and its environs. Radio splashings that are heard from very long distances are able to give rise to the mergers of neutron stars. However, in early March, the situation again became mysterious. It seems that there can still be different types of fast radio splashes. We bring to your attention the historical excursion of Alexei Levin on this topic.

Two astronomy cosmos

European astronomy until the second half of the 16th century had an extremely stable object of study. All the heavenly bodies known to her performed periodic movements in the sky, which were considered manifestations of the eternal world order. If the visible paths of the planets were rather complex and demanded explanations, then the stars of the night after night drawn the same paths in heaven, remaining unchanged both in brightness and among. The only exception was comets, but the scientists after Aristotle considered them a purely atmospheric phenomenon.

This paradigm received the first blow on November 11, 1572. That evening, the future great astronomer-observer quietly noticed a bright star in the constellation Cassiopei, which had never been there before. He traced the gradual attenuation of her luster until completely fading away in March 1574. Even before that, he published the book De Nova Stella , which thundered throughout Europe. So the first of the European scientists found that in the sphere of motionless stars, as it was called, unexpected changes can happen. And a few years later, he proved that the comets belong to the Narous world.

It was only the beginning. In August 1596, the German pastor and the excellent astronomer David Fabritsius noted that one of the stars of the constellation Kita began to dull and by October disappeared from sight in order to shine in the former brilliance in a few months. Its discovery showed that stars can not only be born again, but also periodically vary their luminosity (now such stars are called variables). After the invention of the telescope in space, they began to open more and more dynamic objects of different nature. This trend manifested itself in full force and entrenched in the 20th century.

Bursts in different ranges

Many cosmic processes show themselves in observations by packages of electromagnetic radiation, which are commonly called bursts (Bursts). Until recently, in the center of interests, astrophysics lay “outbreak” impulses of high frequencies-gamma radiation and x-ray. Their energy can reach truly fantastic meanings. For example, on September 16, 2008, the Fermi Space Telescope was registered by a gamma-ray gamma with an isotropic energy equivalent of 8.8x1047 joules, which corresponds to annihilation of about five solar masses. On March 19, 2008, the SWIFT space observatory noticed a gamma-ray, accompanied by such a bright flash of visible light that within 30 seconds a successful observer could see it with a simple eye, although the distance to the source was 7.5 billion light years!

The duration of the gamma-vaplesov varies from less than a hundred milliseconds to tens of minutes. X -ray bursts also demonstrate a strong spread in duration. By the way, in September last year, the echo of the merger of two black holes can be called gravitational-wave surge.

Cosmos fired at the Earth and radio capuls. They can have many sources-radio bulbs, long-wave tails of gamma-ray gamma, gas emissions and plasma from active nuclei of galaxies and close double systems (jets). In 2007, an international team led by a professor at the University of West Virginia Duncan Lorimer reported detecting a powerful package of radio waves lasting less than 5 ms. Its source was in the heavenly sphere 3 ° south of the center of the Small Magellanic Cloud and clearly did not belong to him or our galaxy (DR Lorimer et al., A Bright Millisecond Radio Burst of ExtragalacTic Origin, Science 318 , 5851, Pp. 777-780 (2 Novmber 2007)).

Since then, 16 more powerful and short single radiosimpulses of non -galactic origin have been identified. They were called fast radio (Fast Radio Bursts, FRBS). There is no doubt that such bursts bear information about cosmic cataclysms or other processes with a very greater release of energy, so their study is of great interest for physics and astrophysics.

Lorimerovsky surge

Very short radio -impulses are not easy to notice immediately after arriving on the radio telescope antenna. Usually they are found by analyzing the observation data archived in computers in many years. Most often, a similar search is carried out in a 1-2 GHz (L Band) frequency range of frequencies traditional for radiostronomy. That is how the first quick radio splash was found, which reached the ground on August 24, 2001. It was not possible to determine the exact distance to the source, but Lorimer and his colleagues approximately appreciated it at 500 megaparsk. This means that the source of the FRB 010824 surge is far beyond the boundaries of the Milky Way, but also the local supercrassing of the galaxies. The distance to it is several orders of magnitude exceeds the maximum distances of about 100 kiloparses, where it has still been able to register the brightest pulses of radio pulsaries.

The Lorimerovsky Radio was detected in the analysis of information collected during scanning the sky in the Magellanic Clouds at a frequency of 1.4 GHz using a 64-meter Australian radio telescope (Parkes Radio Telescope). The same telescope caught almost all the other bursts with the exception of only two: FRB 121102, which on February 11, 2012 detected the 300-meter radio-telescope of the Aresibo Observatory in Puerto Rico (Lg Spitler et al . , Fast Radio Burst Discovered in the Arcibo Purecibo Alfa Survey , Astrophys . BURST, Nature 528 , 523-25 ​​(24 December 2015)).

To understand the mechanism of quick radio, it is very important to know the distance to the sources. Until recently, it was possible to evaluate them only on the basis of data on the difference in the time of registration of splash components, having different frequencies. On the way from the source to the ground, it passes through the cold ionized electronic gas, filling the intergalactic space. The distribution speed in this environment of radio waves with different lengths is not the same, this is a well -known phenomenon of dispersion. The short -wave components of the surge move a little faster and therefore reaches the Earth a little earlier than the long -wave. Thus, along the way to the Earth, the surge is blurring, and its measured length turns out to be larger than the one that was at the time of generation. The value of the delay depends on the integrated density of the electrons on the path of the surge (the so -called dispersion measure) and, with other equal ones, grows along with the length of this path. Astrophysical models allow you to calculate this density for different intergalactic distances, that is, for different values ​​of red displacement. However, specific calculations of this kind require a number of preliminary assumptions and therefore give very approximate estimates of distances to sources. Without knowing the distance to the surge source, it is impossible to determine the amount of energy thrown into space during its generation, and, therefore, it is impossible to determine its nature.

April luck

However, last spring, scientists strongly fed. On April 18, 2015, Evan Kin and his colleagues registered everything on the same Australian telescope of the FRB 150418 burst (0.8 ± 0.3) milliseconds a few seconds after his arrival (Keane Ef et al., The Host Galaxy of a Fast Radio Burst, Nature 530, Nature 530 453-456 (25 February 2016) -www.nature.com/nature/journal/v530/n7591/full/nature17140.html ). This made it possible to quickly connect the commands of other radio insatorials that took up the search for the source. Although almost all of these efforts did not give anything, one group of Australian radiostronomers still revealed a weakening radio emission attributed to the residual activity of the surge source (the possibility of accidental coincidence, according to the Kin group, did not exceed two tenths of percent). This radiation was observed for another six days, after which its intensity decreased to the level of ordinary galactic radio shum.

Immediately after the alleged identification of the source, the 820-centimeter telescope “Subaru”, located at the Hawaiian peak of Mauna-Kaa, entered into business. During the observations, on April 19 and 20, its equipment found an elliptical galaxy with a red shift Z = 0.492 ± 0.008 in a given direction, which is removed from us by 1.8 gigaperseck (approximately 6 billion light years). Without optical observations, such accuracy in determining the distance could not be achieved. The mass of the galaxy is approximately 100 billion solar masses.

These results immediately gave an exit to the cosmology. Knowing the distance to the source and the measurement of the surge, the authors of the article were able to estimate the number of free electrons along the line of its movement. This, in turn, made it possible to evaluate the density of the ionized bario substance in the intergalactic space, which is 90% of the entire baronic matter of the universe. The result is well consistent with the data of the WMAP space observatory (Wilkinson Microwave Anisotropy Probe) and with a standard cosmological model (λcdm model).

The discoverers of the FRB 150418 surge calculated that the energy price of its generation was 8x1031 joules, which is approximately equal to the two -day release of solar energy. The luminosity of the surge is estimated at at least 1035 watts and, therefore, a billion times higher than the luminosity of the sun. These are very modest indicators against the background of the scale of gamma-ray, but still we are talking about processes with giant energy release.

The nature of the FRB 150418 source is still in question. Since the elliptical galaxies are mainly filled with old stars, Keen and his colleagues believe that the intricate was generated by a single cataclysm, most likely a clash and a fusion of two compact stars.

However, the conclusions of Kin and its co -authors have already encountered objections. Employees of the Harvard-Smitan Center for Astrophysics Edo Berger and Peter Williams believe that the galaxy, from which, allegedly, a surge has come, can generate a pulsating radio radiation interpreted by the Kin group as a surveillance of the surge itself (http://arxiv.org/abs/1602.08434). They estimate the probability of this at least 10%. If they are right, then the FRB 150418 post is hung in this galaxy in the air. Evan Kin has already stated that his group conducts repeated studies, the results of which will be published ( www.nature.com/news/fresh-over-origins-off-nigmatic-raadio-wave-blasts-1.19494 ). So you need to follow the news.

A new surprise

The saga about fast radio splashes received another sequel. A week after the article on the FRB 150418 article, the same magazine reported on the Internet about detecting repeating bursts: L G. Spitler, P. Scholz et al., A Repeating Fast Radio Burst, Nature , Publice Online 2 March 2016). This indicates that quick radio supports are most likely generated by sources of various nature.

Repeating bursts were opened as part of the search for radio packages in the plane of the galaxy on the radio -telescope in Aresbo (Palfa Survey), during which FRB 121102 was previously registered. In May and June 2015, a new scan of this site was carried out, which revealed ten quick radio splashes with about the same measure of dispersion. This suggests that behind the FRB 121102 and newly open bursts are the same source in the constellation of the charioteer.

Repeated bursts were discovered by Paul Scholz, graduate student of Canadian University McGill, working under the leadership of Professor Astrophysics Victoria Kaspi. He told me that the collaboration participants, in principle, allowed such an opportunity, but considered it unlikely. As expected, they announced the opening only after a thorough study of primary data and conducting control tests. The analysis of the structure of new bursts made it possible to evaluate the distance to the source - about 3 billion light years, however, according to Paul, this figure is very approximate. It has not yet been possible to connect it with any specific galaxy visible in optical telescopes. Perhaps this can be done in the future with the help of radio interferometers.

The origin of the newly discovered radiovples is still unclear. Obviously, these bursts, unlike single, require some permanent source and therefore cannot occur as a result of cataclysis events. The collaboration members suggest that the source is a very young, highly somagnet neutron star, which sometimes generates giant non -periodic outbursts of radio radiation. It is these outbreaks that reach the ground, while the less powerful stable radiation of the young radio pulsar is lost in space due to its enormous remoteness. But, of course, so far it is only a hypothesis.