Double record for GRB 130427A: is the event that produced the highest energy photons ever observed, and he shined in gamma rays for more than 20 hours. The gamma-ray burst was followed and studied by researchers around the world with the best telescopes in space and on Earth. The enormous amount of data collected today is presented in four articles published in the journals Science and online in The Astrophysical Journal in which several researchers have collaborated with INAF. Alexander Maselli, post-doc of IASF of Palermo is the first author of the Science study coordinated by the Italian Swift Team.
Source: www.svs.gsfc.nasa.gov; Credit: NASA/DOE/Fermi LAT Collaboration
A star ends its evolution cycle, and collapses in the huge explosion that follows makes a huge amount of energy. Similar events are very frequent in the universe, but it is rare to find that they are at the same time so close, intense and long-lasting as the gamma-ray burst (GRB) which took place on April 27 and recorded by Fermi, Swift, NuStar and Agile with the support of many observers from Earth. GRB 130427A – this is the theme of the event – was first identified by the instrument GBM (Gamma-ray Burst Monitor) aboard NASA’s Fermi orbiting observatory. Simultaneously, the Large Area Telescope ( LAT ) aboard the Fermi mission always revealed an intense flux of high-energy gamma photons , also recording the photon energy greater than ever associated with a gamma-ray burst : well 94 GeV ( gigaelectronvolt , billions of electron volts) , or about forty billion times greater than the energy carried by photons of light radiation. In addition to being very intense, GRB 130427A also has had an emission of gamma photons very long, as evidenced by the records of the LAT telescope; it observed the GRB for about 20 hours and found a peak in the initial instants of gamma-ray radiation in the same time when some Earth -based telescopes, including those in the design RAPTOR (Rapid telescopes for Optical Response) recorded a flash of visible light.
“The exceptional brilliance of the event, along with the quantity and quality of data collected by different observers, allowed us to test the theories proposed to explain these bursts of emission, showing that none of them is able to explain all the details that have been observed,” says Patrizia Caraveo, INAF – Institute of Space Astrophysics and Cosmic Physics in Milan, Italy responsible for the Fermi- LAT. “It’s one thing that is not surprising, because it is finding the weak points that improve the models.”
The rapid response with which this synergy of observations has been initiated within a few minutes from the revelation of the lightning was also credited with another “hunter of gamma-ray bursts”, which is the NASA’s Swift satellite. “Once we receive the alerts sent from the satellite to the computer I went for an early analysis of the data,” recalls Alexander Maselli, post-doc of INAF – IASF of Palermo, this is part of the Swift Team from Italy. “The results produced, the most important of which is the extremely precise measurement of the position of the “afterglow”, were quickly made available to the international scientific community. The observations made by a large number of telescopes, starting from a few minutes after the burst, produced a large quantity of circular for many days to follow. “
“We quickly realized that this was an extraordinary event, and in the following days we spent all our time analyzing the data that Swift continued to collect. The intensity of the event was such as to enable us exceptionally detailed study of its X-ray emission, as never before had been possible,” insists Giancarlo Cusumano, manager and coordinator of Team Swift at the INAF – IASF of Palermo.