30 November 2011

Christmas burst puzzles

On 25 December 2010, NASA’s Swift satellite detected an unusually bright and long-lived gamma-ray burst. Astrophysicists from DARK and their colleagues explain the unusual phenomenon in a new paper published in Nature.

This illustration shows end phase of the model proposed by Chrisina Thöne and her collaborators. A neutron star may have merged with its binary companion - a massive helion star - and triggered an eruption of gamma rays, shown here. (Aurore Simonnet, NASA E/PO, Sonoma State University).

Gamma-ray bursts (GRBs) are the most powerful explosions in the Universe, and they usually last a few minutes.  The GRB observed on the 25th of December 2010 lasted more than 30 minutes - longer than most GRBs that have been observed.  In addition, it behaved in an atypical manner, and it was not possible to measure its distance. Those things combined led the team to several different theories.

Christina Thöne, who is a post doctoral researcher at the Astrophysical Institute of Andalucía (IAA)n Granada, Spain, completed her PhD at DARK in 2008 and was a guest researcher earlier this year at the Niels Bohr International Academy while she was working on these results.  She led the research on this unknown type of GRB together with Antonio de Ugarte Postigo, who until September this year was a DARK Fellow at the Centre, and is now also at IAA in Granada. 

Dr. Thӧne says she and her colleagues considered “all kinds of weird theories” before settling on the stellar merger scenario.  The evidence shows that possibly a neutron star slowly spirals in toward a massive helium star, eventually colliding and producing a cataclysmic explosion of gamma rays. Then, a faint supernova goes off roughly 10 days later, an event that could explain bumps in the Christmas gamma-ray burst’s fading light curve. 

Read more:
Article in Nature >>