View Full Version : Researchers May have found why classical Novae Erupt in Gamma Rays

7th November 2014, 10:22
Submitted by Busta Sebetseba on Fri, 10/10/2014 - 12:03

According to researchers with NASA's Fermi Gamma-ray Space Telescope, they detected gamma rays from various classical novae a few months ago. These thermonuclear eruptions take place on the surface of white dwarfs that are consuming too much gas off a companion star.
The gamma rays confused researchers: classical novae should not generate these high-energy photons. Gamma rays come from particles accelerated at shock fronts. That means that stuff in the burst's outflow is slamming into other stuff in the outflow.
Radio observations of V959 Monocerotis, one of the Fermi novae, now recommend that it is the difference in the white dwarf's outflow that is to blame, but it's not technically the white dwarf's fault. It is because these stellar corpses are in binary systems.
To reach this conclusion, Laura Chomiuk Michigan State University and colleagues used many radio arrays to monitor V959 Mon. The signal they firstly picked up not only match out-flowing warm gas, but also synchrotron radiation.
Synchrotron release comes from particles accelerated to near-light speeds in the same way as gamma rays do. But radio emission remains a lot longer, and it's visible with much higher resolutions.
Observations spread over many months revealed something interesting. About four months later, the team detected knots of synchrotron release, moving outward from the explosion. The outflow itself was in clear bipolar shapes, with its dumbbell pointing east-west. But after 16 months, the brightest region was still bipolar but indicating north-south. Essentially, it appeared that outflow pattern had rotated 90 degrees.
The dwarf didn't literally spin its ejecta. Here is what may have happened when the white dwarf went nova, it first emitted out fairly thick warm gas in a spherical shell around itself and its companion. As the gas flowed past the stellar companion, it created a bow wave around the star. At the same time, gas pulled on the star. So afterwards when the white dwarf blew out a fast wind, the thick stuff funneled that wind out along the poles.
Shocks were created at the boundaries between the slower, thick outflow and the faster, thin outflow. These shocks produce the outward-moving knots of synchrotron. After the outburst turned off, the bright polar outflows floated away and scattered.

Read more: http://newstonight.co.za/content/researchers-may-have-found-why-classical-novae-erupt-gamma-rays#ixzz3INQl6fiA