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Date and Time of the Query: 2019-05-27 T03:19:00 PDT
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For refcode 1999MNRAS.304...52R:
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NED Abstract

Copyright by Royal Astronomical Society. 1999MNRAS.304...52R The X-ray properties of the nearby LINER galaxy NGC 4736 T. P. Roberts, R. S. Warwick and T. Ohashi Accepted 1998 November 9. Received 1998 September 22; in original form 1998 July 13 ABSTRACT NGC 4736 is a nearby Sab spiral galaxy, hosting one of the closest examples of a low-ionization nuclear emission-line region (LINER) nucleus. We have utilized recent observations by ROSAT and 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, {GAMMA} ~ 1.7), with thermal emission (kT = 0.1-0.6 keV) dominant below 2 keV. An Fe K{alpha} line may also be present at ~ 6.8 keV. There is no evidence for X-ray temporal variability on time-scales of hours to years. A plausible model is that the hard continuum originates in a near-quiescent active galactic nucleus (with L_X_~ 6 x 10^39^ erg s^-1^, 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 excluded. Key words:galaxies: individual: NGC 4736 - galaxies: nuclei - X-rays: galaxies
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