Gamma rays reveal the speed of microquasar SS 433's jets
An international team including scientists from the University of Innsbruck led by Anita Reimer and Olaf Reimer has measured the jets of the galaxy microquasar SS 433 using the HESS gamma-ray telescopes in Namibia. As the researchers reported in the journal Science, this object is one of the most effective particle accelerators in our Milky Way Galaxy.
SS 433 is one of the most exciting objects in our Milky Way Galaxy. Here, the black hole absorbs material from a nearby companion star. This creates a hot accretion disk, a rotating disk that moves the material toward the center. The system produces outward-directed streams of matter — called jets — that move away from the accretion disk in the opposite direction at about a quarter of the speed of light.
Science fiction author Arthur C. Clark's Seven Wonders of the World in a 1997 BBC television series. SS 433 was called the only astronomical object. At the end of the 1970s, SS 433 was observed by Which is reminiscent of a manatee – called fog.
SS 433 is a binary star system in which a black hole with a mass about ten times that of the Sun and a star of similar mass but much larger orbit each other every 13 days. Because of the intense gravitational field, material flows from the star's surface toward the black hole, where it first accumulates in a hot gas disk before finally falling into the black hole. Two combined streams of matter are ejected perpendicular to the plane of the disk at a speed of about one-fourth the speed of light.
The particles are accelerated to extremely high energies
These outbursts from SS 433 can be detected at radio and X-ray wavelengths up to about a light-year away on either side of the central binary star, at which point they become too faint to be seen. But surprisingly, the jets suddenly reappear as bright sources of X-rays about 75 light-years away from their starting point. The reasons for this appearance have long been unclear.
In 2018, the High Altitude Water Cherenkov Gamma-ray Observatory (HAWC) succeeded for the first time in detecting very high-energy gamma rays emanating from the jets of SS 433. So, somewhere in the jets, particles are being accelerated to extremely high energies. It was not clear how or where the particles in the jets were accelerated. Similar questions apply to relativistic jets that originate from the centers of active galaxies (such as quasars). However, the jets coming from SS 433 are much smaller than those coming from extragalactic galactic nuclei, so they are “microquasars.”
Studying gamma-ray emission from quasars offers a key advantage: Although SS 433's jets are 50 times smaller than those of the nearest active galaxy, Centaurus A, their apparent size in the sky is much larger, with SS 433 being a thousand times closer. Once. Earth-like Centaurus A. This allows for more precise spatial measurement of the gamma-ray emission from these jets using modern gamma telescopes.
The speed of external jets has been determined for the first time
Members Hess co After an extensive observing campaign, the extent of gamma-ray emission from SS 433 jets has now been measured. While gamma-ray emission cannot be detected in the central region of the binary star system, emission in the outer jets occurs suddenly at a distance of about 75 light-years on either side of The binary star, similar to previous X-ray observations. The observation of a shift in the position of gamma-ray emission depending on the energy was surprising. Gamma photons with higher energies above 10 TeV are detected as the jets suddenly reappear. However, regions emitting gamma rays with lower energies appear farther up in the jets.
“This is the first-ever observation of the energy dependence of gamma-ray emission from an astrophysical plane,” says Laura Oliveira Neto of the Max Planck Institute for Nuclear Physics in Heidelberg and a graduate of the University of Innsbruck who led the HESS study. SS 433. “We were initially surprised by these results. The concentration of such high-energy photons at locations where X-ray jets reappear indicates efficient acceleration of particles at locations where this had not been expected before.” From this, the speed of the external jets can be extracted for the first time. The difference between this speed and the speed at which the jets are fired indicates that the mechanism that led to the particles being accelerated outward is a strong shock – a very sudden change in the properties of the medium. Hence the presence of the shock would also provide a natural explanation for the reappearance of flows in X-rays: accelerated electrons also produce X-rays
“When these fast particles collide with light quanta, they release part of their energy – this is how the high-energy gamma photons observed at HESS are created. This process is called the inverse Compton effect,” explains Anita Reimer, head of the HESS Research Center. Theoretical Astroparticle Physics Working Group at the University of Innsbruck and a member of the HESS collaboration. “There has been much speculation about the occurrence of particle acceleration in this unique system in our Milky Way Galaxy. The result of our research now allows us to investigate the location of the acceleration and the motion of the jets generated by the black hole.” confirms Olaf Reimer, Chairman Experimental Particle Physics Working Group at the University of Innsbruck, who has led participation in the HESS trial in Austria since 2009.
Hess Observatory
High-energy gamma radiation from Earth can only be observed using a trick. When gamma rays penetrate the atmosphere, they collide with atoms and molecules and create new particles that hurtle toward the Earth like an avalanche. These particles emit flashes lasting only a few billionths of a second (Cherenkov radiation) and can be observed on Earth using large, specially equipped telescopes. So high energy gamma astronomy uses the atmosphere like a giant fluorescent tube. the Hess Observatory, located in the Khomas Highlands of Namibia at an altitude of 1,800 metres, officially entered service in 2002. It consists of an array of five telescopes. There are four telescopes with a mirror diameter of 12 meters at the corners of the square, and another telescope with a diameter of 28 meters is in the middle. This allows the detection of cosmic gamma rays in the range from a few tens of GeV to a few tens of TeV. For comparison: visible light has energies ranging from 2 to 3 MeV. HESS is currently the only instrument observing the southern sky in high-energy gamma light, and it is also the largest and most sensitive telescope system of its kind.
Publication: Acceleration and transport of relativistic electrons in microquasar jets SS 433 HESS Collaboration. Science 383(6681), 402-406, DOI: 10.1126/science.adi2048
Für weitere Informationen zu dieser Pressemeldung kontaktieren Sie bitte: Univ.-Prof. Dr. Anita Reimer Institut für Astro- und Teilchenphysik Universität Innsbruck +43 512 507 52090 [email protected] www.uibk.ac.at/astro/ Univ.-Prof. Dr. Olaf Reimer Institut für Astro- und Teilchenphysik Universität Innsbruck +43 512 507-52060 [email protected] www.uibk.ac.at/astro/ Dr. Guillem Marti-Devesa Institut für Astro- und Teilchenphysik Universität Innsbruck [email protected] Christian Flatz Büro für Öffentlichkeitsarbeit Universität Innsbruck +43 512 507-32022 [email protected] www.uibk.ac.at
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