Classified as an ultraluminous X-ray source (ULX), the object is only the second ever seen in M31 and became the target of an intense observing campaign by orbiting X-ray telescopes -- including NASA's Swift -- and radio observatories on the ground. These efforts resulted in the first detection of radio-emitting jets from a stellar-mass black hole outside our own galaxy.
The ULX's radio-emitting jet (center) is unresolved in this image constructed from Very Long Baseline Array data. Each side of the image is 20 milliarcseconds across, or about the width of a human hair seen from a distance of half a mile. Credit: NRAO/M. Middleton et al.
A ULX is thought to be a binary system containing a black hole that is rapidly accreting gas from its stellar companion. However, to account for the brilliant high-energy output, gas must be flowing into the black hole at a rate very near a theoretical maximum, a feeding frenzy that astronomers do not yet fully understand.
"There are four black hole binaries within our own galaxy that have been observed accreting at these extreme rates," said Matthew Middleton, an astronomer at the Anton Pannekoek Astronomical Institute in Amsterdam. "Gas and dust in our own galaxy interfere with our ability to probe how matter flows into ULXs, so our best glimpse of these processes comes from sources located out of the plane of our galaxy, such as those in M31."
As gas spirals toward a black hole, it becomes compressed and heated, eventually reaching temperatures where it emits X-rays. As the rate of matter ingested by the black hole increases, so does the X-ray brightness of the gas. At some point, the X-ray emission becomes so intense that it pushes back on the inflowing gas, theoretically capping any further increase in the black hole's accretion rate. Astronomers refer to this as the Eddington limit, after Sir Arthur Eddington, the British astrophysicist who first recognized a similar cutoff to the maximum luminosity of a star.
"Black-hole binaries in our galaxy that show accretion at the Eddington limit also exhibit powerful radio-emitting jets that move near the speed of light," Middleton said. Although astronomers know little about the physical nature of these jets, detecting them at all would confirm that the ULX is accreting at the limit and identify it as a stellar mass black hole.
The European Space Agency's XMM-Newton observatory first detected the ULX, dubbed XMMU J004243.6+412519 after its astronomical coordinates, on Jan. 15. Middleton and a large international team then began monitoring it at X-ray energies using XMM-Newton and NASA's Swift satellite and Chandra X-ray Observatory. The scientists conducted radio observations using the Karl G. Jansky Very Large Array (VLA) and the continent-spanning Very Long Baseline Array, both operated by the National Science Foundation in Socorro, N.M., and the Arcminute Microkelvin Imager Large Array located at the Mullard Radio Astronomy Observatory near Cambridge, England.
Black holes have been conclusively detected in two varieties: "lightweight" ones created by stars and containing up to a few dozen times the sun's mass, and supermassive "heavyweights" of millions to billions of solar masses found at the centers of most big galaxies. Astronomers have debated whether many ULXs represent hard-to-find "middleweight" versions, containing hundreds to thousands of solar masses.
"The discovery of jets tells us that this particular ULX is a typical stellar remnant about 10 times the mass of the sun, swallowing as much material as it possibly can," Middleton said. "We may well find jets in ULXs with similar X-ray properties in other nearby galaxies, which will help us better understand the nature of these incredible outflows."
Commenting on the findings on behalf of the Swift team, Stefan Immler at NASA's Goddard Space Flight Center in Greenbelt, Md., noted that it was almost exciting enough for astronomers to witness a new ULX so close to home, even if "close" is a few million light-years away. "But detecting the jets is a real triumph, one that will allow us to study the accretion process of these elusive black hole candidates in never-before-seen detail," he said.Francis Reddy
Francis Reddy | EurekAlert!
Tracking down the 'missing' carbon from the Martian atmosphere
25.11.2015 | California Institute of Technology
Iowa State astronomers say comet fragments best explanation of mysterious dimming star
25.11.2015 | Iowa State University
Fraunhofer ISE demonstriert neue Zell- und Modultechnologien an der Außenfassade eines Laborgebäudes
Das Fraunhofer-Institut für Solare Energiesysteme ISE hat die Außenfassade eines seiner Laborgebäude mit 70 Photovoltaik-Modulen ausgerüstet. Die Module...
The Fraunhofer Institute for Solar Energy Systems ISE has installed 70 photovoltaic modules on the outer façade of one of its lab buildings. The modules were...
Normalerweise werden Unterwasser-Roboter über lange Kabel von Booten oder von Land aus gesteuert. Forschern der Jacobs University in Bremen ist nun ein Durchbruch in der Mensch-Maschine-Kommunikation gelungen: Erstmals konnten sie einen Unterwasser-Roboter mit Hilfe von Gesten navigieren. Eine spezielle Kamera half dabei, die Zeichensprache in Befehle umzusetzen. Die Feldtests fanden im Rahmen des EU-geförderten Projektes CADDY „Cognitive Autonomous Diving buddy“ statt.
Archäologische Untersuchungen im Ozean und vergleichbare komplexe Forschungsprojekte unter Wasser sind auf die Unterstützung von Robotern angewiesen, um in...
Nerve cells cover their high energy demand with glucose and lactate. Scientists of the University of Zurich now provide new support for this. They show for the first time in the intact mouse brain evidence for an exchange of lactate between different brain cells. With this study they were able to confirm a 20-year old hypothesis.
In comparison to other organs, the human brain has the highest energy requirements. The supply of energy for nerve cells and the particular role of lactic acid...
Die Simulation von Prozessen bei der Lasermaterialbearbeitung ist in den letzten Jahren immer besser geworden. Die Software kann heute relativ gut voraussagen, was am Werkstück passiert. Leider ist sie hochkomplex und erfordert viel Rechenzeit. Durch eine clevere Vereinfachung können Experten vom Fraunhofer-Institut für Lasertechnik ILT erstmals eine Simulationssoftware anbieten, die Prozesse in Echtzeit rechnet und auch auf Tablets oder Smartphones läuft. Mit der schnellen Software lassen sich teure Versuche einsparen und noch besser optimale Prozessparameter finden.
Eine verlässliche Simulation von Laserprozessen war bislang eine Sache für Experten. Mit ausgefeilten Software-Paketen und viel Zeit auf Computerclustern...
25.11.2015 | Veranstaltungen
25.11.2015 | Veranstaltungen
25.11.2015 | Veranstaltungen