Interstellar scintillation evidence for relativistic expansion in low-frequency variable sources

Details Interstellar scintillation evidence for relativistic expansion in low-frequency variable sources Interstellar scintillation evidence for relativistic expansion in low-frequency variable sources

Sep 1978

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1978apj...224..835c&link_type=abstract

Astrophysical Journal, Part 1, vol. 224, Sept. 15, 1978, p. 835-840.

Astronomy and Astrophysics

Astrophysics

39

Extragalactic Radio Sources, Radiant Flux Density, Radio Spectra, Relativistic Velocity, Scintillation, Astronomical Models, Autocorrelation, Brightness Temperature, Interstellar Matter, Synchrotron Radiation

Scientific paper

Interstellar scintillation should cause fluctuations with characteristic bandwidths of 100,000 Hz at 0.43 GHz in the spectra of sufficiently compact extragalactic sources. No such fluctuations were detected in spectral observations of a number of compact and low-frequency variable sources, and 3-sigma upper limits of approximately 0.001 were set to their scintillation indices. These limits indicate that the angular diameters of DA 406, CTA 102, and 3C 454.3 are greater than 0.0002 arcsec at 0.43 GHz and that the low-frequency variations of these sources cannot be due to any reasonable number (less than 100,000) of components smaller than 10 to the -7th power arcsec. If these sources are at their redshift distances, they are larger than their light-travel sizes and are expanding relativistically, regardless of the emission mechanism. Since this result removes the main justification for invoking new high-brightness mechanisms, incoherent electron-synchrotron radiation in relativistically expanding regions is probably responsible for low-frequency variability.

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