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A. Zezas, G. Fabbiano (Harvard-Smithsonian CfA), M. Ward (U of Leicester), A. Prestwich, S.S. Murray (Harvard-Smithsonian CfA)
We present a detailed study of the discrete sources detected in the Chandra observations of two well known star-forming galaxies. In both objects we detect a large number of sources with diverse properties. The majority of them are identified as X-ray binaries, based on their spectra (and variability in the case of M82). However, there is a number of very soft and/or extended sources which are identified with supernova remnants. We also discuss the properties of the discrete sources in optical, radio and infrared wavelengths in order to further understand their nature and connect them with the stellar populations in these galaxies. A very important result is the confirmation of previous indications that there is a population of sources with X-ray luminosities much higher than the Eddington limit for a 1M\odot compact object, suggesting that they are associated with black hole binaries in the 10-1000M\odot mass range. Here, we present evidence that indeed these sources are most probably X-ray binaries and we study their temporal and spectral properties as an attempt to connect this new population with the well known galactic X-ray binaries. We also compare the stellar populations in these two star-forming galaxies with other normal galaxies (M31, M81) or early type galaxies (e.g., NGC 4697). We combine the X-ray results with stellar evolutionary synthesis modeling in order to study the starburst component of the composite galaxies and the population of ultraluminous sources in the star-forming galaxies.
The author(s) of this abstract have provided an email address for comments about the abstract: azezas@cfa.harvard.edu