Modulation of the IR and the X-ray emission gives us the orbital period of the binary, only 4.8 hours." Fortunately, we can see it at infrared (IR) wavelengths and that's how we know it's a Wolf-Rayet star, from the IR spectral lines. "We can't see Cygnus X-3 optically because it's in the galactic plane where optical extinction by interstellar dust obscures the source. These types of stars have a very vigorous stellar wind, and that's probably what's driving things in this source." Wolf-Rayet stars are massive stars - 7 to 50 solar masses - that have blown away their outer envelope of hydrogen. "It's the only case known of a Wolf-Rayet star with a compact companion. "Cygnus X-3 may be the first example of a blazar here in our own galaxy," he continued. The accreting gas heats up and shines brightly as an X-ray source. Gas from a massive star feeds the accretion disk of an orbiting black hole or neutron star. Left: An artist's concept of a high-mass x-ray binary system like Cygnus X-3. This likely makes Cyg X-3 a galactic blazar - a jet source where we were looking straight down the jet." "Two days later it extended to 120 milliarcseconds and then it disappeared. "When we looked at the images, lo and behold, there was definitely a one-sided radio jet, about 50 milliarcseconds long," recalled McCollough. It's also a very bright radio source that undergoes massive flares from time to time."ĭuring an intense flare in 1997, McCollough and colleagues made a high-resolution radio map of Cygnus X-3 using the Very Long Baseline Array (VLBA), a continent-sized radio interferometer. "Because of the deep gravity well, a huge amount of energy can be released in x-rays and gamma-rays. "Cygnus X-3 is a black hole or a neutron star that's accreting matter from an companion star," explains Mike McCollough of the NASA/Marshall Space Flight Center. The answers to some of these questions about distant galaxies may lie right here in our own Milky Way, in the binary star system Cygnus X-3. What accelerates the material in the jets to relativistic speeds? How are the jets collimated? What are they made of? Many aspects of blazars remain a mystery. Among all AGNs, blazars can be detected over the widest range of frequencies, from radio waves to gamma rays. When one of these beams is pointed toward Earth, it looks especially bright and astronomers call it a blazar. They produce narrow beams of energetic particles and magnetic fields, and eject them outward in opposite directions away from the disk at nearly the speed of light. The cores of these systems, called active galactic nuclei (AGNs), outshine all of the stars in the host galaxy by factors of 10 to 1000.Ībout 10% of all AGNs are stranger still. As gas in the accretion disk falls into the hole it heats up and glows so brightly in x-rays that we can detect them a billion light years away. Gigantic disks of gas - called accretion disks - swirl around central black holes that weigh in at millions or even billions of solar masses. It's a classic case of truth being stranger than fiction. Febru- Astronomers are increasingly convinced that supermassive black holes lie at the centers of most large galaxies.
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