Abstract
NGC 4736 is a nearby Sab spiral galaxy, hosting one of the closest examples of a lowionization nuclear emission-line region (LINER) nucleus. We have utilized recent observations by ROSATand ASCA to characterize the X-ray properties of this galaxy. 12 discrete X-ray sources are detected within the region subtended by its optical disc, the majority of which are likely to be X-ray binaries associated with the galaxy. By far the brightest source in the X-ray band is positionally coincident with the nucleus of the galaxy and is spatially resolved into a component with a radial extent of ,3 kpc plus a point-like core. The broad-band (0.1±10 keV) spectrum of this nuclear source is composed of a hard continuum with a spectral slope characteristic of that observed in classical Seyfert nuclei (i.e. power-law photon index, G < 1:7), with thermal emission (kT 0:1±0.6 keV) dominant below 2 keV. An Fe Ka line may also be present at ,6:8 keV. There is no evidence for X-ray temporal variability on timescales of hours to years. A plausible model is that the hard continuum originates in a nearquiescent active galactic nucleus (with LX , 6 10 erg s, 0.5±10 keV) embedded in the LINER at the centre of NGC 4736. However, an alternative explanation, namely that the LINER is the site of a dense population of X-ray binary sources, cannot be completely
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