SIMBAD references

X-ray emission (L_x∼2.5x10³⁹erg/s) from the nearby, face-on Magellanic-type irregular galaxy NGC 4449 was detected with the ROSAT PSPC and HRI. The HRI resolves seven point sources located within the D₂₅ ellipse of the galaxy. The most luminous source is a supernova remnant detected with an intrinsic luminosity of L_x=4.7x10³⁸erg/s. Another very luminous source (L_x=3.1x10³⁸erg/s) is located between two Hα shells. A source near the southern border of the galaxy (L_x=1.7x10³⁸erg/s) shows flux variations between the HRI and PSPC observations of a factor of two, no counterparts in other wavelengths and most likely is an X-ray binary. Two fainter sources (L_x=1.2x10³⁸erg/s and L_x=0.8x10³⁸erg/s) are positioned at the border of regions that show enhanced blue emission. The center of the galaxy was detected with a luminosity of L_x=7x10³⁷erg/s. Combining the spatial resolution of the HRI and the spectral capabilities of the PSPC indicates that the total X-ray emission of NGC 4449 is composed of resolved point sources (L_x=1.4x10³⁹erg/s), unresolved point sources (L_x=2x10³⁸erg/s), and extended emission possibly arising from a hot (T∼3x10⁶K) gaseous component of the interstellar medium (L_x=1.0x10³⁹erg/s). The spectral and spatial findings indicate that most of the thermal emission originates from parts in the outer HI disk and above it. The parameters and implications of a possible gaseous halo component are discussed. The NGC 4449 X-ray emission components are compared with those of the Magellanic Clouds which can be resolved in the contributing X-ray emission components. The NGC 4449 point source and extended emission components seem to reflect the LMC scaled for the different galaxy masses.