Microquasar helps unravel secrets of Universe’s brightest beacons

Many years of observations of the micro-quasar SS 433 have made it possible to identify the details of the processes responsible for the production of high-energy radiation and to better understand its distant massive cousins: quasars, reports the IFJ PAN.

During observations of the SS 433 microquasar made at the High-Altitude Water Cherenkov Gamma-Ray Observatory (HAWC), gamma rays with energies above 25 TeV were recorded for the first time. Careful analysis of the data, in turn, has led to surprising conclusionsow regarding the sites and mechanism ofoin responsible for the production of this radiation. The findings have just been presented in the pages of a prestigious scientific journal "Nature".

The research was reported by the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Krakow, Poland, ktorego employees participated in the study.

Quasars – as emphasized by the IFJ PAN – are among the most unusual and at the same time brightest objectsoIn the Universe. The driving force behind the quasar is the supermassive black hole at its center, surrounded by an accretion disk formed by falling matter.

Quasars are the source ofod with extremely intense electromagnetic radiation, ktore covers almost the entire spectrum: from radio waves to high-energy gamma rays. However – as a type of galactic nuclei – quasars are by definition objects distant from us. The closest sposrod of them, driven by frantically spinning wokoł itself with the supermassive black hole Markarian 231, hosted in the nucleus of a galaxy 600 million distantoin light-years. Unfortunately, this is not a distance conducive to high-resolution observations, whichore would facilitate understanding of the nature of the processes involvedow.

However, scientists may resort to observations. quasaroin miniature. As noted by the IFJ PAN, what a quasar does on the scale of a galaxy, a microquasar does on the scale of a stellar system.

Markarian 231 black holes are gigantic: the smaller one has a mass of 4 millionoin solar masses, greater as much as 150 millionow. In contrast, the closest microquasar to us, located in the background of the Eagle constellation SS 433, is a system of subojnym of radically smaller size. There is a very dense object here – probably a black hole with the mass of several suns, which is a remnant of a supernova explosion. It devours matter from an accretion disk fueled by stellar winds flowing in from a nearby super giant of spectral type A (a similar star, perfectly visible in the night sky, is Deneb, the brightest object of the Swan constellation). All this picturesque vapor, spinning wokoł itself at an impressive rate of 13 days and surrounded by the W50 nebula, is separated from Earth by a distance of only 18 thousand. light years.

– Zaroquasars, as well as microquasars, can generate jets, i.e. very narrow and very long streams of matter, emitted in both directions along the object’s rotation axis, explains Dr. hab, quoted in the press release. Sabrina Casanova, prof. IFJ PAN. – Jets are created by particles accelerated to speeds often close to the speed of light. In terms of velocity, however, the jets from SS 433 are not particularly impressive: they reach only 26 percent of the. speed of light.

However, as Dr. hab emphasizes. Casanova, something else is more important here. – Most of the observed quasarsow has jets more or less, but nevertheless directed toward us. This orientation makes it difficult to rozrothe glow of particularołow. The SS 433 microquasar, on the other hand, was kind enough to point its jets not toward us, but almost perpendicular to the direction in which theorym we are looking. So not only do we have the object almost "at hand", it is still positioned optimally when it comes to observing such details as where radiation is generated, the researcher states.

SS 433 is one of only a dozen or so quasarsow found in our galaxy – and on top of that, it is one of the few to emit gamma radiation. For 1017 days, the radiation was recorded at the HAWC observatory, operating at an altitude of over 4100 m n.p.m. On the slope of the Mexican volcano Sierra Negra. The detector built here consists of 300 steel tanksoin with water, equipped with photomultipliers sensitive to fleeting flashes of light, known as Cherenkov radiation. It appears in the reservoir when a particle moving faster than the speed of light in water falls into it.

The key point is that some of the flashesoin comes from particles generated by collisions of high-energy quantaoin gamma rays with Earth’s atmosphere. Proper analysis of the flashesoin the reservoirs makes it possible to identify their cause. In this wayob Each day, the HAWC indirectly records gamma photons with energies ranging from 100 gigaelectronvoltsow (GeV) up to 100 tera-electronvoltow (TeV). These are at energies up to a trillion times greater than the energy of photonoin visible light and several times the energy of protonoin the LHC gas pedal.

During observations of SS 433 (conducted at the limit of the HAWC’s resolving capabilities), the scientists managed to register photons with energies above 25 TeV, i.e. 3 to 10 times larger than those reported throughout the history of microquasar researchow. To the surprise of researchers in the high-energy gamma-ray range, the brightest object in the system was not SS 433 itself at all – but the sites on either side of it, in which theorych jets break off, colliding with matter rejected by the supernova.

– This is not the end of the surprises, adds Dr. Francisco Salesa Greus of the IFJ PAN, quoted in the release. – Gamma photons with energies of 25 TeV must be produced by particles with even higher energies. They could be protons, but then they would have to have huge energies, on the order of 250 TeV. From the data collected, however, it appeared that this mechanism, even if it actually works, in the case of SS 433 is not able to generate enough gamma rays, explains the scientist.

In further work, data from the HAWC were matched with measurements of SS 433 in other spectral ranges from other observatoriow. Ultimately, it was established that high-energy gamma quanta – Or at least most of them – must be emitted by electrons in the ditto as they collide with the low-energy microwave background radiation filling the entire cosmos. The above mechanism – first described just in the article in the "Nature" – not mohead be detected in quasar observationsow with jets pointing toward Earth. Microquasar SS 433 pomohead thus reveal not only their own secrets, but also the secrets of the Universe’s brightest beacons.

Sourceosource: PAP – Science in Poland, fot. HAWC Observatory, J. Goodman. Pictured is the High-Altitude Water Cherenkov Gamma-Ray Observatory.