Oxygen and Iron Abundances in Nearby Galaxies Using Ultraluminous X-ray   Sources
  We determined oxygen and iron abundances of the interstellar medium (ISM) using K-shell (O) and L-shell (Fe) X-ray photo-ionization edges towards Ultra luminous X-ray sources (ULXs). We determine the hydrogen column densities (n_H) towards the ULXs from XMM-Newton archival spectra of 14 ULX sources. We compare our X-ray values with those obtained from radio HI observations for 8 of the sources. The X-ray model n_H values are in good agreement with the HI n_H values, implying that the hydrogen absorption towards the ULX is not local to the source, with the exception of M81 X-1. Oxygen abundances and iron abundances are roughly solar for the host galaxies. 
Lisa M. Winter, Richard F. Mushotzky and Christopher S. Reynolds