XMM-Newton and Chandra observations of X-ray sources in nearby galaxies

X-ray astronomy is an important branch of high energy astrophysics and deals with the cosmic X-ray emissions from celestial objects. Cosmic X-rays come from the sources where several astrophysical processes accelerate particles to relativistic energies and heat the medium to temperatures of millions of degrees exists. Since 1970?s, the study of X-ray sources in nearby galaxies have been started with the X-ray observatories that have been launched. Natures of these sources have became possible to discuss by examining their X-ray properties and radiation processes. With the new generation observatories XMM-Newton and Chandra launched in 1999, the X-ray studies have been carried out nowadays with more extensively.In this thesis, X-ray point-like sources in selected three nearby (< 10 Mpc) galaxies (NGC 4631, NGC 4490/4485 and NGC 4945) have been examined using XMM-Newton and Chandra archive data. If the sources have enough data to analyze then their nature have been disscussed by examining their X-ray spectra and timing variations.