A recent study by an international team of astronomers has revealed new insights into the enigmatic Cygnus X-3 binary system, located about 24,000 light-years away in the Milky Way galaxy. Using Nasa’s Imaging X-ray Polarimetry Explorer (IXPE), researchers have discovered that this system, which likely contains a black hole and a massive Wolf-Rayet star, exhibits an X-ray emission pattern similar to some of the most luminous quasars in the universe.
Cygnus X-3 was first detected in the early 1970s through powerful radio jets that periodically switch on and off. Despite being shrouded in thick dust that obscures it in visible light, further observations in radio, infrared, and X-ray wavelengths have revealed that it is an X-ray binary system. This involves 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 Space.com report said.
One of the key findings from the study, led by Alexandra Veledina of the University of Turku in Finland, is that the X-ray emission 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.”
The system’s luminosity is particularly intriguing because it appears to break the Eddington Limit, a theoretical threshold that dictates how much matter can be accreted by a black hole before radiation pressure stalls 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 found that the degree of polarization in the X-ray light varies with the system’s activity, reaching 24.9 per cent during its ULX phase and dropping to 10.4 per cent 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.
The team’s findings, published in the journal Nature Astronomy, offer a closer model for understanding distant ULXs and provide a framework for future observations aimed at catching the predicted funnel collapse in real-time.
Cygnus X-3 was first detected in the early 1970s through powerful radio jets that periodically switch on and off. Despite being shrouded in thick dust that obscures it in visible light, further observations in radio, infrared, and X-ray wavelengths have revealed that it is an X-ray binary system. This involves 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 Space.com report said.
One of the key findings from the study, led by Alexandra Veledina of the University of Turku in Finland, is that the X-ray emission 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.”
The system’s luminosity is particularly intriguing because it appears to break the Eddington Limit, a theoretical threshold that dictates how much matter can be accreted by a black hole before radiation pressure stalls 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 found that the degree of polarization in the X-ray light varies with the system’s activity, reaching 24.9 per cent during its ULX phase and dropping to 10.4 per cent 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.
The team’s findings, published in the journal Nature Astronomy, offer a closer model for understanding distant ULXs and provide a framework for future observations aimed at catching the predicted funnel collapse in real-time.
