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

Abstract

view Abstract Citations (40) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Interstellar scintillation evidence for relativistic expansion in low-frequency variable sources. Condon, J. J. ; Dennison, B. Abstract 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. Publication: The Astrophysical Journal Pub Date: September 1978 DOI: 10.1086/156432 Bibcode: 1978ApJ...224..835C Keywords: Extragalactic Radio Sources; Radiant Flux Density; Radio Spectra; Relativistic Velocity; Scintillation; Astronomical Models; Autocorrelation; Brightness Temperature; Interstellar Matter; Synchrotron Radiation; Astrophysics; Interstellar Matter:Scintillations; Radio Sources: Variations full text sources ADS | data products SIMBAD (9)