What Is the Accretion Rate in NGC 4258?

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Abstract
We estimate the accretion rate onto the black hole in the nucleus of NGC 4258. The result is model dependent. We find that a thin disk that is flat out to 2 × 103GM/c2 (M≡black hole mass) and that has inclination equal to that of the masing disk must have 0.01 M☉ yr-1 for consistency with near-infrared data. A thin disk that is warped at ~103GM/c2 requires 1.5 × 10-4 M☉ yr-1 for consistency with near-infrared data. Reasonable warp models and the near-infrared data are not consistent with as low as the 7 × 10-5α M☉ yr-1 proposed by Neufeld & Maloney. An advection-dominated flow model combined with the X-ray data implies 0.01 M☉ yr-1. Consistency with a tight 22 GHz upper limit on the flux from the central source requires a transition radius of ~(10-100)GM/c2, although the 22 GHz upper limit may be relaxed by appeal to free-free absorption. Physical conditions in the observed VLBI jet features can also be related to conditions in the inner accretion flow. We conclude with a list of observations that might further constrain .
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