XMM-Newton and Chandra observations of SHEEP sources
  We present Chandra and XMM observations of 12 bright (f(2-10 keV)   > 10^-13 cgs) sources from the ASCA SHEEP (Search for the High Energy   Extragalactic Population) survey. Most of these have been either not observed or not detected previously with the ROSAT mission and therefore they constitute a sample biased towards hard sources. The Chandra observations are important in locating with accuracy the optical counterpart of the X-ray sources. Optical spectroscopic observations show that our sample is associated with both narrow-line (NL) (six objects), and   Broad-Line (BL) AGN (five objects) with one source remaining unidentified.   Our sources cover the redshift range 0.04 to 1.29 spanning luminosities from 10^42 to 10^45 cgs (2-10 keV). The NL sources have preferentially lower redshift (and luminosity) compared with the BL ones. This can be most easily explained in a model where the NL AGN are intrinsically less luminous than the BL ones in line with the results of Steffen et al.   The X-ray spectral fittings show a roughly equal number of obscured (N_H>10^22 cgs) and unobscured (N_H<10^22 cgs) sources.   There is a clear tendency for obscured sources to be associated with   NL AGN and unobscured sources with BL ones. However, there is a marked exception with the highest obscuring column observed at a BL AGN at a redshift of z=0.5. 
I. Georgantopoulos (National Observatory of Athens), K. Nandra   (Imperial College), M. Brotherton (University of Wyoming & ...