Second binary system confirmed to be a gamma ray source

Using the Fermi Gamma-ray Space Telescope, a Russian astronomer has purportedly discovered new evidence confirming that binary systems that have strong colliding stellar winds, also known as colliding wind binaries (CWBs), are indeed a source of high-energy gamma radiation.

Writing in the latest issue of Monthly Notices of the Royal Astronomical Society Letters, Maxim Pshirkov of the Lomonosov Moscow State University Sternberg Astronomical Institute reported that CWBs, binary star systems in which the both members are massive stars that emit powerful, radiatively-driven stellar winds, have long been considered a possible gamma ray source.

However, only one had ever been detected: Eta Carinae, a system located about 8,000 light years from Earth. Since one source was not enough to verify that binary stars emit high-energy gamma radiation, however, scientists have been searching for additional sources – which proved to be no easy feat, Pshirkov said, as recent calculations proved that such stars are “incredibly rare.”

Three years ago, a team of American and Austrian researchers compiled a list of seven different star systems which contained hot and highly luminous Wolf-Rayet stars, making them candidates for areas where radiation could be detected. In his study, Pshirkov analyzed seven years of data from the Fermi telescope and discovered another possible source of gamma radiation.

System’s proximity helped with the discover, astronomer says

The source in question, Gamma Velorum, is a multiple star system located in the constellation Vela that contains stars of 30 and 10 solar masses. It is also the closest and brightest Wolf-Rayet star and one of the most luminous stars in the night sky, and now, thanks to Pshirkov’s research, it has been confirmed as a “source of gamma-radiation at 6.σ. confidence level.”

Gamma Velorum is approximately 200,000 times more luminous than the sun, and it possesses strong stellar winds with an extremely high mass loss rate of one hundred-thousandth and two ten-millionth of the solar mass every year, the Moscow astronomer said in a statement. As the stellar winds in the system collide, they are travelling at speeds of more than 1,000 kilometers per second, which causes particles to become accelerated through unknown means.

It was this acceleration that was detected using the Fermi telescope, and the detection, which has a statistical accuracy of six standard deviations, is said to be “definitely reliable,” the university explained in a statement. Pshirkov credited the fact that the Gamma Velorum system “lies above the plane surface and it is comparatively close to us” as part of the reason for his success.

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