The First Optical Validation of an X-Ray Line-emitting Object: A Detection in the XMM-Newton Observation of the Chandra Deep Field-South

We present the first optical validation of an X-ray line-emitting object (XLEO) discovered in the XMM-Newton observation of the Chandra Deep Field-South. The object is an active galactic nucleus at z_X~0.66. An optical spectrum of the source indeed confirms and refines (z_o=0.665) the redshift obtained from the X-ray line. The X-ray and optical properties of the source are presented and discussed.

Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.