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VLBI Observations of Gamma-Ray-Quiet Active Galactic Nuclei: Comparing Radio-Core Brightness Temperatures

journal contribution
posted on 2023-05-16, 11:06 authored by Tingay, SJ, Murphy, DW, James LovellJames Lovell, Costa, ME, Peter McCullochPeter McCulloch, Edwards, PG, Jauncey, DL, Reynolds, JE, Tzioumis, AK, King, EA, Jones, DL, Preston, RA, Meier, DL, van Ommen, TD, Nicolson, GD, Quick, JFH
We present VLBI and Australia Telescope Compact Array images and derive source-frame radio-core brightness temperatures for three prominent, flat-spectrum extragalactic radio sources, notable because they have not been detected as gamma-ray sources with the EGRET instrument. Radio-core brightness temperatures are discussed as an indicator of relativistic beaming. A comparison of source-frame radio-core brightness temperatures for EGRET-identified and gammaray-quiet, radio-loud AGNs shows that a wide range in beaming properties is likely to exist, independent of the level of gamma-ray emission. This comparison suggests that, although there is a strong relationship between radio emission and gamma-ray emission in EGRET-identified AGNs, and many EGRET-identified AGNs show evidence for relativistic beaming, there is little evidence for a one-to-one correspondence between the strength of gamma-ray emission and the degree of beaming of the radio emission. © 1998. The American Astronomical Society. All rights reserved.


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The Astrophysical Journal








School of Natural Sciences


The American Astronomical Society

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