The ROSAT view of NGC 1365: core emission, the highly variable source NGC 1365--X1 and alignments of surrounding X-ray sources

Abstract

We present a spectral and spatial analysis of the nuclear and circumnuclear X-ray emission of the prominent southern starburst/Seyfert galaxy NGC 1365. To describe the X-ray spectrum of the core source, we favour a two-component model consisting of about equally strong contributions from a Raymond-Smith plasma (with ~cosmic abundances) and a powerlaw. The origin of both components is discussed, and a detailed comparison of the X-ray properties with multi-wavelength observations of NGC 1365 and a large sample of type-I AGNs is performed. Among the surrounding X-ray sources we focus on an analysis of the enigmatic source NGC 1365-X1, which is one of the most luminous and most highly variable off-nuclear X-ray sources known so far. Positions of further X-ray sources in the field of view are derived and it is briefly pointed out that all HRI sources (except one) are `aligned' relative to the central source.