Probing the Mystery of Hours-long Celestial Explosions
Scientists at the University of Leicester have shed light on the origin of so-called “ultra-long Gamma Ray bursts”, in results to be presented at a meeting in Russia next week.
“Gamma-ray bursts, or GRBs, are the most powerful explosions in the universe,” explained Dr. Phil Evans, the lead author of the study, which has also been published in the Monthly Notices of the Royal Astronomy Society. “But they’re also normally short-lived; lasting from a few seconds up to tens of minutes. However a small number of them have been found to continue for much longer. GRB 130925A, which was the starting point of our work, lasted for over 5 hours!”
Gamma Ray Bursts arise when a massive star collapses to a black hole. The US/UK/Italian satellite “Swift”, which detected its 900th Gamma Ray Burst last week, was designed to study these phenomena.
Professor Julian Osborne, the head of the Leicester Swift team, said: “Swift has given us a very rich dataset, allowing us to compare GRB 130925A with normal GRBs. We show that ultra-long bursts can be explained if the space around them has much less gas in it than that around normal GRBs. That means that the type of star which collapsed was probably a large blue supergiant, which throws off less material in its middle age than the more compact stars that normally cause GRBs.”
This result was found using a combination of the Swift satellite, which celebrates 10 years in orbit this November, and the US/Russian mission Konus-Wind, which has its 20th birthday celebratory conference in St Petersburg next week.
Professor Dick Willingale, a co-author of the study from the University of Leicester, said: “Not only is this result significant scientifically, but it shows the importance of international collaborations to build observatories, and of sharing information between those observatories.
“We could not have reached our conclusions without the Swift and Konus teams working together, and it’s fitting that it comes as they both celebrate major anniversaries.”
Additional Details:
The Swift project is managed by the NASA Goddard Space Flight Center; the satellite is operated by the Pennsylvania State University in collaboration with the Los Alamos National Laboratory in New Mexico and Orbital Sciences Corp. in the USA. The United Kingdom and Italy are Swift project collaborators, the mission also includes contributions from Germany and Japan. UK involvement in Swift is funded by the UK Space Agency, which supports the University of Leicester XRT calibration and UK Swift Science Data Centre (http://www.swift.ac.uk), and the Mullard Space Science Laboratory contributions to the Swift UV/Optical Telescope.
Publication:
GRB 130925A: AN ULTRALONG GAMMA RAY BURST WITH A DUST-ECHO AFTERGLOW, AND IMPLICATIONS FOR THE ORIGIN OF THE ULTRALONG GRBS
P. A. Evans, R. Willingale, J. P. Osborne, P. T. O’Brien, N. R. Tanvir, D. D. Frederiks, V. D. Pal’shin, D. S. Svinkin, A. Lien, J. Cummings, S. Xiong, B.-B. Zhang, D. Goetz, V. Savchenko, H. Negoro, S. Nakahira, K. Suzuki, K. Wiersema, R. L. C. Starling, A. J. Castro-Tirado, A. P. Beardmore, R. Sanchez-Ramirez, J. Gorosabel, S. Jeong, J. A. Kennea, D. N. Burrows, N. Gehrels.
Monthly Notices of the Royal Astronomy Society, 444, 250 (17pp) 2014 October.
http://mnras.oxfordjournals.org/content/444/1/250
Image: The X-ray image of GRB 130925 from the Swift X-ray Telescope. The white object in the centre is the Gamma Ray Burst. The large diffuse region to the right is a cluster of galaxies. The other objects are X-ray emitting celestial objects, most likely supermassive black holes as the centres of distant galaxies. The full image is approximately the size of the full moon.
