New Study Sheds Light on Cygnus X-3 Binary System’s Unique X-ray Emissions
An international team of astronomers has made groundbreaking discoveries about the enigmatic Cygnus X-3 binary system, located approximately 24,000 light-years away in the Milky Way galaxy. By utilizing NASA’s Imaging X-ray Polarimetry Explorer (IXPE), researchers have found that this system, likely comprising a black hole and a massive Wolf-Rayet star, exhibits an X-ray emission pattern akin to some of the most luminous quasars in the universe.
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Cygnus X-3
Cygnus X-3 was first detected in the early 1970s through its powerful radio jets, which periodically switch on and off. Despite being shrouded in thick dust that obscures it in visible light, subsequent observations in radio, infrared, and X-ray wavelengths revealed it to be an X-ray binary system. Such systems involve the transfer of matter between a massive star and a compact object, either a neutron star or a black hole, orbiting a common center of gravity.
A key finding from the study, led by Alexandra Veledina of the University of Turku in Finland, is that the X-ray emission from Cygnus X-3 is amplified by a funnel-shaped cavity surrounding the probable black hole. Veledina explained, “We have discovered that the compact object is surrounded by an envelope of dense, opaque matter. The light that we observe is a reflection off the inner funnel walls formed by the surrounding gas, resembling a cup with a mirror interior.”
This discovery is significant because the system’s luminosity appears to break the Eddington Limit, a theoretical threshold that dictates how much matter can be accreted by a black hole before radiation pressure halts further infall. Cygnus X-3’s behavior is similar to ultra-luminous X-ray sources (ULXs) found in distant galaxies, whose emissions are magnified by a surrounding funnel.
The study also found that the degree of polarization in the X-ray light varies with the system’s activity, reaching 24.9 percent during its ULX phase and dropping to 10.4 percent when less active. This variation suggests that the funnel structure changes with the amount of accretion. If the rate of infalling material decreases significantly, the funnel can collapse, only to reform when accretion picks up again.
These findings, published in the journal Nature Astronomy, offer a closer model for understanding distant ULXs and provide a framework for future observations aimed at capturing the predicted funnel collapse in real-time.
