The nuclear spectral energy distribution of NGC 4395, the least luminous type 1 Seyfert galaxy

We present X-ray (ROSAT), infrared, and radio observations of NGC 4395, which harbors the optically least luminous type 1 Seyfert nucleus discovered thus far. In combination with published optical and ultraviolet spectra, we have used these data to assemble the broadband spectral energy distribution (SED) of the galaxy's nucleus. Interestingly, the SED of NGC 4395 differs markedly from the SEDs of both quasars and typical low-luminosity active galactic nuclei, which may be a manifestation of the different physical conditions (i.e., black hole masses, accretion rates, and/or accretion modes) that exist in these objects. The nuclear X-ray source in NGC 4395 is variable and has an observed luminosity of just similar to 10(38) ergs s(-1). Although this emission could plausibly be associated with either weak Seyfert activity or a bright stellar-mass binary system, the galaxy's optical and ultraviolet emission-line properties strongly suggest that the X-rays arise from a classical active galactic nucleus.