| 24th of October 2016 |
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| First γ-ray binary in the LMC |
| by Phil Edwards (CASS) |
| Using data from NASA's Fermi Gamma-ray Space
Telescope, the Australia Telescope Compact Array (ATCA), and other facilities,
an international
team of scientists has found the first γ-ray binary in another galaxy
and the most luminous one ever seen. The dual-star system, dubbed LMC P3,
contains a massive star and a crushed stellar core that interact to produce a
cyclic flood of γ-rays, the highest-energy form of light. LMC P3 lies
within the expanding debris of a supernova explosion located in the Large
Magellanic Cloud (LMC), a small nearby galaxy about 163,000 light-years away.
In 2012, the Chandra X-ray satellite revealed a strong X-ray source within the supernova remnant. In 2015, a team led by Robin Corbet, began looking for new γ-ray binaries in Fermi data by searching for the periodic changes characteristic of these systems. They discovered a 10.3-day cyclic change centred near an unidentified γ-ray point source called LMC P3. Were they the same object? To find out, Corbet's team observed the binary in X-rays using NASA's Swift satellite, at radio wavelengths with the ATCA near Narrabri and in visible light using a 4.1-m telescope in Chile and a 1.9-m telescope in South Africa. The Swift observations clearly reveal the same 10.3-day emission cycle seen in γ-rays by Fermi. They also indicate that the brightest X-ray emission occurs opposite the γ-ray peak, so when one reaches maximum the other is at minimum. Radio data exhibit the same period and out-of-phase relationship with the γ-ray peak, confirming that LMC P3 is indeed the same system investigated by Chandra. - These results were published in ApJ earlier this month. This article uses material from the original NASA press release. Image credit: NASA |