Astrophysicists Detect Destruction Of Three Stars By Black Holes b4in.org/g6xA Researchers from Moscow Institute of Physics and Technology (MIPT) and the Space Research Institute of the Russian Academy of Sciences have reported registering three possible occasions of thetidal destruction of stars by supermassive black holes at the centers of galaxies. Details are given in an article by IldarKhabibullin and Sergei Sazonov, accepted for publication by the Monthly Notices of the Royal Astronomical Society journal (a preprint is available at arXiv.org). The astrophysicists used data obtained by X-ray orbiting observatories ROSAT and XMM-Newton. The former was put into orbit in 1990 and served until 1999, when XMM-Newton took over. The two satellites gathered enough information to detect very rare events, the destruction of stars by supermassive black holes. A star in a galaxy passes by a black hole closely enough to be destroyed once every 10,000 years. It is possible to detect the death of a star in a fairly distant galaxy as the destruction of a star generates a bright X-ray flare; it is only necessary to distinguish such a flare from other types of X-ray radiation. Because flares occur in a variety of astrophysical processes, the task of finding stars destroyed by black holes is quite complicated. The researchers developed a number of methods to distinguish the destruction of a star by a black hole from other occurrences. The easiest way to filter out extraneous signals is to eliminate from consideration flares in our galaxy; there is only one supermassive black hole at the center of the Milky Way, so there clearly could not have been stars that have become victims of gravity on the periphery of our galaxy. The researchers also excludedsourcesof radiation that were too large (in angular measurements)and additionally analyzed the range of objects along with the dependence of brightness on time. Since a supermassive black hole takes just a few years to fully absorb the captured matter of a destroyed star (typically, this makes up about a quarter of its original mass), observations repeateda decade later should detect significant dimming of an X-ray source. The researchers obtained sky survey data in the 1990s and in the 2000s, so they were able to detect objects whose brightness reduced by at least tenfold. More b4in.org/g6xA
Posted on: Tue, 12 Aug 2014 20:21:28 +0000
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