Sun, Jul 24, 2011 - Page 2 News List

Taiwanese astronomers find gamma ray emissions in Southern Cross binary star

TO INFINITY AND BEYOND:The research group said that the discovery could reveal much more about the interactions between a massive star and a neutron star

By Lee I-chia  /  Staff Reporter

Astronomers in Taiwan recently discovered gamma ray emissions in a binary star system in the Southern Cross.

The discovery was made by a research team led by professor Albert Kong (江國興) of National Tsing Hua University’s Institute of Astronomy and Department of Physics in collaboration with academics in Hong Kong and South Korea.

According to the National Science Council, which funded the six-member research team, the discovery was made in October last year. The results of that work were published in the Astrophysical Journal Letters on Wednesday, ahead of a group of 173 US researchers who had also discovered the phenomenon.

The team said most binary systems are composed of two stars or a massive star with a white dwarf — a small star composed mostly of electron-degenerate matter and is very dense. However, the binary system, labeled PSR B1259-63/LS 2883, that the group has been observing is composed of a star nine times larger than the sun and a neutron star about the size of Hsinchu City.

Tam Pak-hin (譚柏軒), group researcher and the initial discoverer of the phenomena, said he had been observing the binary star since October when the neutron star approached the star and observed the rare gamma ray emission in mid-November.

“Because the signal was too weak, the discovery was questioned by other astronomers,” he said, adding that “surprisingly, we discovered the rays beginning from January and the signal was many times stronger than the previous [observation].”

“It is an unprecedented discovery and there is currently no recognized explanation,” he added.

Another researcher, Regina Huang (黃修慧), said that “in the past, astronomers have used radio waves and X-rays to observe this binary system, but no one had ever found gamma rays measuring 1 billion electron volts.”

X-rays have electron wave bands in the thousands of electron volts, Huang added.

The group said the discovery could help tell us more about the interaction mechanism between a massive star and neutron star.

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