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VLBA Continuum Observations of NGC 4258: Constraints on an Advection-Dominated Accretion Flow

J. R. Herrnstein·L. J. Greenhill·J. M. Moran·P. J. Diamond·M. Inoue·N. Nakai·M. Miyoshi
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Abstract

We report a 3 sigma upper limit of 220 microJanskys on any 22-GHz continuum emission coincident with the central engine in NGC 4258. If NGC 4258 is powered by an advection-dominated accretion flow, this radio upper limit implies that the inner advection-dominated flow cannot extend significantly beyond about 100 Schwarzschild radii.

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J. R. Herrnstein, L. J. Greenhill, J. M. Moran, P. J. Diamond, M. Inoue, N. Nakai, M. Miyoshi. 1998-02-20. VLBA Continuum Observations of NGC 4258: Constraints on an Advection-Dominated Accretion Flow. https://doi.org/10.1086/311284

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