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M.E. Sulkanen (NASA/MSFC & U. Michigan), J.N. Bregman (U. Michigan)
Recently it has been argued that the hard x-ray power-law tails exhibited in the spectra of several nearby giant elliptical galaxies are consistent with the existence of low-radiative efficiency accretion flows (ADAFs) onto a massive black hole in the centers of the galaxies. The expected fluxes from these central ADAFs as derived from x-ray spectral analyses indicate that they may be visible as x-ray point sources. We analyze archival ROSAT HRI images of three such galaxies, NGCs 1399, 4636, and 4696, to determine whether such ADAF sources are detected. No x-ray point source at the centers of these galaxies that would be associated with such a central ADAF appear to be found. The measured upper limits for the fluxes of a central x-ray point source in these clusters will also be presented.