NASA’s Swift spacecraft has detected a gamma-ray burst, called GRB 111209A, which is one of the longest events of this kind ever observed.
The duration of gamma-ray emission from GRB 111209A was approximately 2 hours.
Swift X-Ray Telescope image of GRB 111209A (Swift team)
An international team of astronomers using the Burst Alert Telescope on-board Swift spacecraft recorded this unusual event on December 9, 2011.
Follow-up observations, started after the Swift alert by teams of the robotic 60-cm REM telescope in La Silla, the Australia Telescope Compact Array, the Russian KONUS instrument on NASA’s Wind satellite as well as the two other instruments on-board Swift probe, allowed astronomers to detect X-ray and optical afterglows, and determine properties of GRB 111209A.
NASA's Swift spacecraft (Gehrels N. et al)
The results, published on the UK Swift Science Data Centre’s website, show that the properties of GRB 111209A are similar to those observed in other long energetic gamma-ray bursts. However, the huge duration of gamma- and X-ray emission makes it exceptional and as unique as GRB 101225A, better known as the Christmas Day burst.
The total isotropic energy of GRB 111209A was estimated at 5.8 × 1053 erg.
Its optical brightness reached an apparent magnitude of about 15.4.
The results also show that the source of this ultra-long gamma-ray burst is located in the constellation of Phoenix in the Southern hemisphere about 8 billion light-years away.
Some researchers say that GRB 111209A may originate from a massive star collapse or can be associated with an active galactic nucleus.
Continued monitoring of the source of GRB 111209A should help clarify its origin.
