OREANDA-NEWS. November 11, 2009. Joint Russian-American KONUS-WIND Space Experiment: Continuos Observation of Gamma-Ray Bursts and Soft Gamma Repeaters within 15 Years.

Joint Russian-American experiment aimed at studying gamma-ray bursts and soft gamma repeaters has been successfully carried out with Russian KONUS scientific instrument onboard American spacecraft WIND since November 1994. The KONUS instrument was designed and manufactured in Ioffe Physical Technical Institute of Russian Academy of Sciences under the supervision of corresponding member of RAS Evgeny Mazets. Co-PI of the joint project from the US side is Dr. Thomas Cline from NASA Goddard Space Flight Center. The WIND spacecraft was launched on November 1, 1994 to the interplanetary orbit between the Earth and the L1 libration point. The instrument was switched on November 11, and since then it has been uninterruptedly observing cosmic gamma-ray bursts - the most grandiose explosions in the Universe. In the common conception, these colossal explosions happen at collapses of massive stars resulting in black hole formation or at merging of two neutron stars or at merging of a neutron star and a black hole. Due to great luminosity, the gamma-ray bursts sources can be detected from enormous distances, from the ancient past when the age of Universe counted only several percents of its present age. Soft gamma repeaters represent rare class of sources emitting soft repeating bursts which are connected with single neutron stars with the most strong magnetic fields. Soft gamma repeaters were discovered in 1979 during Ioffe Institute investigations onboard the VENERA interplanetary missions.

The KONUS-WIND instrument is high sensitive in a wide energy range; it is featured by the program optimized for registration of temporal and spectral parameters of gamma-ray bursts and has the opportunity to observe the whole celestial sphere at the absence of regular disturbances which are common for near Earth orbits. For the fifteen years the large massive of information about more than 3500 bursts and about the activity of all known soft gamma repeaters has been obtained. Here we would like to emphasize only the registration and the study of unique giant gamma-repeater flares in our Galaxy SGR1900+14, SGR1627-41, SGR1806-20 and the discovery of giant gamma repeater flares in the neighbor galaxies M81 and M31. It is supposed that such giant bursts are accounted for a global restructuring of neutron star magnetic field with a repeater emitting in gamma rays brighter than the entire Galaxy. It should be especially underlined that thanks to the optimal observation conditions in KONUS-WIND experiment none of those important and interesting bursts were omitted.

Russian-American KONUS-WIND experiment takes one of leading places in the research of X-ray and gamma radiation from bursts in wide energy range 20 keV-10 MeV. Its data on light curves, energy spectra, spectral variability are widely called for and they are an integral part of modern broadband studies of cosmic gamma-ray burst sources. A striking examples of effectiveness of such studies are the results obtained at investigating optical and gamma-ray emission of bursts August 20, 2005 and March 19, 2008 which are based on the gamma-ray data of the KONUS-WIND experiment. The results of these studies made it possible to determine for the first time that optical and gamma emission of the bursts is generated at the same location and to find the ratio between this two components of burst emission. The data of these observations are published in Nature magazine.

The research of the cosmic gamma-burst nature as the most powerful in Universe objects with an extremely high energy release is one of the most actual problems in fundamental space research. Scientific programs of NASA near-Earth observatories SWIFT and Fermi are dedicated to this problem. The synchronous observations of KONUS-WIND together with these observatories significantly supplement obtained data grace to the unique opportunity to permanently observe the whole celestial sphere.

Altogether by the KONUS-WIND experiment results more than 50 collaborative articles have been published in refereed scientific journals, more than 30 cooperative reports are made at international scientific conferences. The KONUS instrument has demonstrated a high level of reliability and allowed to gain a number of new unique scientific data on gamma-ray bursts. The results of express analysis of the experimental data are regularly published at international electronic circular GCN of NASA Goddard Space Flight Center and are available at the internet site of Ioffe Institute. The KONUS-WIND experiment clearly demonstrated the effectiveness of the international cooperation by example of investigation of most unusual and mysterious phenomena in modern astrophysics.

The collaborative experiment is carried out in cooperation between Federal Space Agency (Russian Federation) and NASA (USA).