1999A&A...352..415I

High-resolution X-ray observations of the face-on galaxy M 83 with the HRI onboard ROSAT are presented. The analysis aimed at studying the X-ray point source population inside the galaxy and disentangling the X-ray emission components (i.e. point sources, extended emission from hot gas in the bulge, disk and halo). Within the D₂₅ ellipse of M 83, 21 X-ray sources are detected with (0.1-2.4keV band) fluxes ranging from 1.4 to 115x10^–14erg/cm²/s, corresponding to luminosities of (1.3-106)x10³⁸erg/s for an assumed distance of 8.9Mpc. The sources account for half (2.0x10⁴⁰erg/s) of the total X-ray luminosity of the galaxy (4.1x10⁴⁰erg/s). Using the high spatial resolution of the HRI instrument and applying a new technique to search for variable sources in the extended bulge region leads to the detection of four variable X-ray sources within the bulge (<1kpc radius from the nucleus). The amount of truly diffuse emission from hot gas represents ≲45% of the total bulge luminosity (1.0x10⁴⁰erg/s). A variable (factor ≳2), super-Eddington (3.8x10³⁹erg/s) X-ray source is found to coincide with a faint, extended optical counterpart. Based on the spectral indices optical-to-X-ray α_OX=1 and radio-to-optical α_RO<0, the source is unlikely to be a background galaxy, AGN or quasar and most likely represents a massive (∼30M_☉) accreting black hole binary, located in a compact HII region or in a globular cluster in M 83. We also detect two luminous (3.7 and 6.7x10³⁸erg/s), previously unknown supernova remnant candidates, located in extended Hα emission complexes and coinciding with compact 6cm and 20cm radio sources. Bright extended X-ray emission is discerned in the south-western spiral arm from point sources and from the overall diffuse emission with the HRI. Spectral analysis of the PSPC data gives evidence for the detection of gas flowing into the halo of the galaxy (soft 0.26keV component, absorbed by the Galactic foreground only), and hot gas (0.95keV) with additional intrinsic absorption, that is heated by the star-forming activity in the south-western spiral arm of M 83.