NRAO: Radio Telescopes Unravel Mystery of Nova Gamma Rays

[bystander]

Radio Telescopes Unravel Mystery of Nova Gamma Rays
National Radio Astronomy Observatory | 2014 Oct 08

A nova does not explode like an expanding ball, but instead throws out gas in different directions at different times and different speeds. When this gas inevitably crashes together, it produces shocks and high-energy gamma-ray photons. The complex explosion and gas collisions in nova V959 Mon is illustrated here. In the first days of the nova explosion, dense, relatively slow-moving material is expelled along the binary star system's equator (yellow material in left panel). Over the next several weeks, fast winds pick up and are blown off the binary, but they are funneled along the binary star system's poles (blue material in central panel). The equatorial and polar material crashes together at their intersection, producing shocks and gamma-ray emission (red regions in central panel). Finally, at later times, the nova stops blowing a wind, and the material drifts off into space, the fireworks finished (right panel). (Credit: Bill Saxton, NRAO/AUI/NSF)

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Highly-detailed radio-telescope images have pinpointed the locations where a stellar explosion called a nova emitted gamma rays, the most energetic form of electromagnetic waves. The discovery revealed a probable mechanism for the gamma-ray emissions, which mystified astronomers when first observed in 2012.

"We not only found where the gamma rays came from, but also got a look at a previously-unseen scenario that may be common in other nova explosions," said Laura Chomiuk, of Michigan State University.

A nova occurs when a dense white dwarf star pulls material onto itself from a companion star, triggering a thermonuclear explosion that blows debris into interstellar space. Astronomers did not expect this scenario to produce high-energy gamma rays. However, in June of 2012, NASA's Fermi spacecraft detected gamma rays coming from a nova called V959 Mon, some 6500 light-years from Earth.

At the same time, observations with the Karl G. Jansky Very Large Array (VLA) indicated that radio waves coming from the nova probably were caused by subatomic particles moving at nearly the speed of light interacting with magnetic fields. The high-energy gamma-ray emission, the astronomers noted, also required such fast-moving particles. ...

Astronomers See Right Into Heart of Exploding Star
University of Manchester | via EurekAlert | 2014 Oct 08

Binary orbits as the driver of γ-ray emission and mass ejection in classical novae - Laura Chomiuk et al

• Nature 514(7522) 339 (16 Oct 2014) DOI: 10.1038/nature13773
  arXiv.org > astro-ph > arXiv:1410.3473 > 13 Oct 2014

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