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MPE News August 18, 2010

News from a nova: gamma rays

For the first time, astronomers have detected gamma-rays from a nova, a finding that surprised both observers and theorists. The discovery using NASA's Fermi Gamma-ray Space Telescope overturns the notion that novae explosions lack the power to emit such high-energy radiation.

Gamma rays are the most energetic form of light, and Fermi's Large Area Telescope (LAT) detected the nova for 15 days. Scientists believe the emission arose as a high velocity shock wave raced from the site of the explosion. A paper detailing the discovery appeared in the journal Science on 13. August 2010.

V407 Cyg
Fermi's Large Area Telescope saw no sign of a nova in 19 days of data prior to 10. March (left), but the eruption is obvious in data from the following 19 days (right).
Credit: NASA/DOE/Fermi LAT Collaboration

The system V407 Cyg lies 9,000 light-years away. The binary system contains a compact white dwarf and a red giant star about 500 times the size of the sun. The white dwarf intercepts and captures some of the outflowing gas from the red giant, which accumulates on its surface and eventually becomes hot and dense enough for the hydrogen to fuse into helium. This energy-producing process triggers a runaway reaction that explodes the accumulated gas. Unlike in a supernova explosion however, the white dwarf itself remains intact.

The magnetic fields of the blast trap particles within the shell and accelerate them to velocities near the speed of light. The gamma rays are probably generated when these accelerated particles smash into the wind from the red giant.

The Max Planck Institute for Extraterrestrial Physics is involved in the scientific analysis of data from the Large Area Telescope onboard Fermi and was responsible for the development of the detectors and the power supplies of its secondary instrument, the Fermi Gamma-ray Burst Monitor (GBM).

Original paper:
Gamma-Ray Emission Concurrent with the Nova in the Symbiotic Binary V407 Cygni
Fermi LAT Collaboration
externer Verweis Science, Volume 329, Issue 5993, pp. 817- (2010)
Other press releases:
external link NASA press release
external link Press release of the University of Hiroshima (in Japanese)

internal link Dr. Hannelore Hämmerle
Press Officer
Max-Planck-Institut für extraterrestrische Physik
phone: +49 89 30000-3980
email: hanneh@mpe.mpg.de

internal link Dr. Andy Strong
Max-Planck-Institut für extraterrestrische Physik
phone: +49 89 30000-3575
email: aws@mpe.mpg.de
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