Astronomy

Continuous Source Quasar

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Science  04 Feb 2000:
Vol. 287, Issue 5454, pp. 769
DOI: 10.1126/science.287.5454.769d

Quasars, or quasi-stellar objects, are compact extragalactic sources that emit tremendous amounts of energy. They are thought to be powered by supermassive black holes surrounded by accretion disks. A small fraction of quasars emit at radio wavelengths, and by studying the variability in the radio emissions, astronomers can learn more about the source and the material through which the emissions travel on their way to Earth.

Dennett-Thorpe and de Bruyn observed the most variable (in radio emissions) quasar, J1819+3845 for 96 hours with the new Westerbork Synthesis Radio Telescope multi-frequency front end receivers (www.nfra.nl/wsrt). They found that the variability is due to interstellar scintillation and that the source of the scattering is probably the Local Bubble, close to Earth. After defining the location of the scatterer, the authors inferred that the source region for most of the flux intensity has less than a 16 microarcsecond radius and that the emissions come from a steady source of outward flowing particles. The steady source may be either a cauldron near the active galactic nucleus where the particles are continuously regenerated or a relativistic jet.—LR

Astrophys. J.529, L65 (2000).

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