A light echo occurs when interstellar gas is heated by radiation and reacts by emission of light. An international team led by Stefanie Komossa of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, the light echo an enormous X-ray flare, which was almost certainly produced when a single star was interrupted by a supermassive black Hole. For the first time, the light echo of such a rare and highly dramatic event could be observed in great detail. The light echo not only shown the stellar interference process, but it also offers a powerful new method for mapping galactic nuclei.
If a star is disrupted by a black hole at the core of a galaxy, the remains will inevitably attracted and absorbed from the black hole. This sudden increase in the accretion leads to a sudden burst of UV and X-ray light, because the gas from the star is disturbed very hot. As the high radiation travels through the core of the galaxy lights surrounding matter and thus makes it possible to probe regions of the galaxy, which would otherwise unobservable.
"To study the nucleus of a normal galaxy, as we look at the New York skyline at night during a power outage: You can not learn much about the buildings, streets and parks," said Stefanie Komossa. "The situation is changing, for example, while a fireworks display. It is exactly the same when a sudden burst of the high radiation of a galaxy is lit." However, the astronomers to hurry up and look through the telescope at the right time, since X-ray bursts is not very long.
From the strength, the level of ionization and the speeds derived from the rapidly changing emission lines, the physicists can tell which part of the galaxy, they are issued. The emission lines represent the "fingerprints" of the atoms in the hot gases heated by the flare. The galaxy catalog called SDSSJ0952 2143 was found in December 2007 by Komossa and her team in the Sloan Digital Sky Survey Archive caught their attention because of its superstrong iron lines: the strongest (relative to oxygen emission), the ever observed in a Galaxy. They are the authors is an indication of a molecular torus, plays an important role in the so-called unified models of active galaxies.
The Unified model posits that all active galaxies are made from identical components and the perceived differences are only due to the different directions from which the galaxies. An important element of this model is the molecular torus, which surrounds the black hole and its accretion disk and covers be, if they come from certain directions. The width of the spectral lines that scientists measure is influenced by the direction and the view is from the molecular torus.
If the expectations of Komossa and her colleagues confirmed, this will be the first time that scientists have seen a strong time-variable signal from a molecular torus. From the easy coverage, the torus can be mapped and its geometry deduce that something was not possible until today.
In the same vein is the detection of variable emission in the infrared band: It can be seen as the "last cry for help" of the heated dusty torus matter before the dust is destroyed by the flash.
In addition to the remarkably strong iron lines, the scientists also found a very peculiar form of hydrogen emission lines, had never before seen. This line information on activities of the disk of matter around the black hole, which consists mainly of hydrogen.
"Probably we will see the rubble disrupted the star is currently accreted from the black hole," says Zhou Hongyan from the MPE, co-author of the research paper.
The recently discovered light echo further and will be prosecuted with powerful telescopes. The burst itself has faded away. The first observations with the Chandra X-ray satellite show measurable already weak X-rays from the galactic core. "Reverberation mapping of light echoes opened new opportunities to study galaxies," concludes Komossa. The team will now use this method to the physical conditions in the circumnuclear material in active and non-active galaxies.
If a star is disrupted by a black hole at the core of a galaxy, the remains will inevitably attracted and absorbed from the black hole. This sudden increase in the accretion leads to a sudden burst of UV and X-ray light, because the gas from the star is disturbed very hot. As the high radiation travels through the core of the galaxy lights surrounding matter and thus makes it possible to probe regions of the galaxy, which would otherwise unobservable.
"To study the nucleus of a normal galaxy, as we look at the New York skyline at night during a power outage: You can not learn much about the buildings, streets and parks," said Stefanie Komossa. "The situation is changing, for example, while a fireworks display. It is exactly the same when a sudden burst of the high radiation of a galaxy is lit." However, the astronomers to hurry up and look through the telescope at the right time, since X-ray bursts is not very long.
From the strength, the level of ionization and the speeds derived from the rapidly changing emission lines, the physicists can tell which part of the galaxy, they are issued. The emission lines represent the "fingerprints" of the atoms in the hot gases heated by the flare. The galaxy catalog called SDSSJ0952 2143 was found in December 2007 by Komossa and her team in the Sloan Digital Sky Survey Archive caught their attention because of its superstrong iron lines: the strongest (relative to oxygen emission), the ever observed in a Galaxy. They are the authors is an indication of a molecular torus, plays an important role in the so-called unified models of active galaxies.
The Unified model posits that all active galaxies are made from identical components and the perceived differences are only due to the different directions from which the galaxies. An important element of this model is the molecular torus, which surrounds the black hole and its accretion disk and covers be, if they come from certain directions. The width of the spectral lines that scientists measure is influenced by the direction and the view is from the molecular torus.
If the expectations of Komossa and her colleagues confirmed, this will be the first time that scientists have seen a strong time-variable signal from a molecular torus. From the easy coverage, the torus can be mapped and its geometry deduce that something was not possible until today.
In the same vein is the detection of variable emission in the infrared band: It can be seen as the "last cry for help" of the heated dusty torus matter before the dust is destroyed by the flash.
In addition to the remarkably strong iron lines, the scientists also found a very peculiar form of hydrogen emission lines, had never before seen. This line information on activities of the disk of matter around the black hole, which consists mainly of hydrogen.
"Probably we will see the rubble disrupted the star is currently accreted from the black hole," says Zhou Hongyan from the MPE, co-author of the research paper.
The recently discovered light echo further and will be prosecuted with powerful telescopes. The burst itself has faded away. The first observations with the Chandra X-ray satellite show measurable already weak X-rays from the galactic core. "Reverberation mapping of light echoes opened new opportunities to study galaxies," concludes Komossa. The team will now use this method to the physical conditions in the circumnuclear material in active and non-active galaxies.
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