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Post Info TOPIC: Cygnus A


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Posts: 131433
Date:
1RXS J195928.7+404405
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Title: Discovery of a Luminous Radio Transient 460 pc from the Central Supermassive Black Hole in Cygnus A
Author: Daniel A. Perley, Richard A. Perley, Vivek Dhawan, Christopher L. Carilli

We report the appearance of a new radio source at a projected offset of 460 pc from the nucleus of Cygnus A. The flux density of the source (which we designate Cygnus A-2) rose from an upper limit of <0.5 mJy in 1989 to 4 mJy in 2016 (nu=8.5 GHz), but is currently not varying by more than a few percent per year. The radio luminosity of the source is comparable to the most luminous known supernovae, it is compact in VLBA observations down to a scale of 4 pc, and it is coincident with a near-infrared point source seen in pre-existing adaptive optics and HST observations. The most likely interpretation of this source is that it represents a secondary supermassive black hole in a close orbit around the Cygnus A primary, although an exotic supernova model cannot be ruled out. The gravitational influence of a secondary SMBH at this location may have played an important role in triggering the rapid accretion that has powered the Cygnus A radio jet over the past 10^7 years.

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Posts: 131433
Date:
PGC 63932
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VLA Reveals New Object Near Supermassive Black Hole in Famous Galaxy

Pointing the National Science Foundation's Very Large Array (VLA) at a famous galaxy for the first time in two decades, a team of astronomers got a big surprise, finding that a bright new object had appeared near the galaxy's core. The object, the scientists concluded, is either a very rare type of supernova explosion or, more likely, an outburst from a second supermassive black hole closely orbiting the galaxy's primary, central supermassive black hole.
The astronomers observed Cygnus A, a well-known and often-studied galaxy discovered by radio-astronomy pioneer Grote Reber in 1939. The radio discovery was matched to a visible-light image in 1951, and the galaxy, some 800 million light-years from Earth, was an early target of the VLA after its completion in the early 1980s. Detailed images from the VLA published in 1984 produced major advances in scientists' understanding of the superfast "jets" of subatomic particles propelled into intergalactic space by the gravitational energy of supermassive black holes at the cores of galaxies.

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RE: Cygnus A
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ATel 9495: Discovery of a Radio Transient in Cygnus A 



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Tutto il cielo di LOFAR

Ideato e gestito dall'Istituto di radioastronomia olandese ASTRON, questo innovativo strumento è destinato a esplorare l'Universo nelle lunghezze d'onda tra i 2 e i 20 metri, una banda finora inaccessibile agli astrofisici, che attendono dunque con ansia l'entrata in funzione a pieno regime di LOFAR. Ma la loro attesa non sarà ancora lunga. E' stata infatti annunciata ieri, al 219° meeting della American Astronomical Society, la possibilità di fare richiesta di tempo di osservazione con questo radio telescopio a partire dal prossimo maggio. E, ancora più importante, è stato annunciato il formale avvio della prima scansione completa di tutto il cielo, il necessario passo iniziale verso quello che rappresenta il principale obbiettivo scientifico di LOFAR, ovvero la mappatura del cielo radio a sensibilità e risoluzioni angolari mai raggiunte a queste basse frequenze.
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Cygnus A (3C 405) is one of the most famous radio galaxies, and among the strongest radio sources in the sky. It was discovered by Grote Reber in 1939. In 1953 Roger Jennison and M K Das Gupta showed it to be a double source. Like all radio galaxies, it contains an active galactic nucleus.
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