A binary star system consisting of a massive star and a probable black hole, which together are a source of intense X-rays, has been shown to be a smaller example of some of the most luminous quasars. the universe.
The new findings of an international team that NASA‘S Imaging X-ray Polarimetry Explorer (IXPE) describe how an X-ray binary star system at a distance of about 24,000 m Light years away in our Milky Way amplifies its X-rays in a funnel-shaped cavity, which is the probable black hole.
The system, Cygnus X-3, was discovered in the early 1970s when radio telescopes detected powerful jets emanating from it at almost the same altitude. Speed of LightThe radio emission from these jets lasts for several days before turning off, only to be turned back on later.
The origin of the jets was a mystery at the time. The system has been described as an “astronomical enigma,” further complicated by the fact that we can’t even see Cygnus X-3 in visible light; it is obscured by thick dust in the plane of our galaxy. In the 1970s, radio astronomers at observatories around the world coordinated their work by telephone to catch Cygnus X-3 turning on or off.
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Over the years, through further observations in the radio, infrared and X-ray ranges, astronomers have determined that Cygnus X-3 is an X-ray binary star system in which matter is transferred between a massive star and a compact object orbiting a common center. HeavyThe compact object is either a Neutron star or, more likely, a black hole with a mass about five times greater than the Mass of our sunThe massive star is a Wolf-Rayet star – a rare phase that Supergiant stars emitting strong stellar winds that carry large parts of their outer shell into SpaceIt is the material that the wind blows away from this Wolf-Rayet star that feeds an accretion disk that spirals around the compact object.
Cygnus X-3s brightness is hard to believe. The flow of matter onto a compact object like a black hole is controlled by a property known as the Eddington limit. When the accretion rate is high enough, the accretion disk becomes a jam – the matter piles up, the disk gets denser and so hot that the amount of radiation escaping can shut off the inflow of fresh material. In this way, black holes can regulate their own growth, and some of the material is spit out again in the radio-emitting jets.
But some of the brightest Quasars — Galaxies with extremely active supermassive black holes in their interiors – appear to exceed the Eddington limit because their luminosity is extremely high, but they still appear to be accreting matter. And Cygnus X-3 appears to fall into this category, albeit on a smaller scale.
Now a team led by Alexandra Veledina of the University of Turku in Finland has used IXPE to measure the degree of polarization of the X-ray light from Cygnus X-3. They found that the degree of polarization is so high that it can only be explained by the X-rays scattered inside a funnel-shaped cavity at the heart of the accretion disk.
“We discovered that the compact object is surrounded by a shell of dense, opaque matter,” Veledina said in a opinion. “The light we observe is a reflection of the inner funnel walls, which are formed by the surrounding gas and resemble a cup with a mirrored interior.”
An opaque shell raised by a funnel-shaped cavity is typical of quasars known as ‘ULXs’ – ultra-bright X-ray sourcesThe magnitude of enhancement due to X-rays scattered from the inside of the funnel cavity is also analogous to ULXs.
“ULXs are typically observed as bright dots in images of distant galaxies, with their emissions amplified by the focusing effects of the funnel surrounding the compact object, acting like a megaphone,” said Juri Poutanen of the University of Turku, a member of the study team. “However, due to the enormous distances to these sources … they appear relatively faint to X-ray telescopes.”
Therefore, learning about ULXs in quasars has proven difficult, but astronomers can now use the much closer Cygnus X-3 as a model to better understand these distant ULXs.
“Our discovery has now revealed a bright counterpart to these distant ULXs, located in our own galaxy,” said Poutanen.
Cygnus X-3’s outbursts are irregular because of the Wolf-Rayet star’s elliptical orbit around the compact object, meaning it is closer at times and more material in the wind falls toward the likely black hole. IXPE was able to determine that the degree of polarization reaches 24.9% when Cygnus X-3 is in its ULX phase – when the amount of infalling material is greatest – while it drops to 10.4% when it is less active. This suggests that the structure of the funnel changes in response to greater or lesser amounts of accretion. If the accretion rate gets too low, the funnel can collapse completely, only to rebuild when accretion increases again, Veledina’s team predicts.
The team is now planning further observations to track this collapse. One indication of this would be a drop in polarization to almost zero, which would suggest that the X-ray emission is coming directly from the hot gas on the surface of the accretion disk and not indirectly through scattering in the funnel.
The results were published in the journal on June 21 Natural astronomy.