Spectroscopic identification of ten faint hard X-ray sources discovered byChandra

We report optical spectroscopic identifications of 10 hard (2-10 keV) X-ray selected sources discovered by Chandra. The X-ray flux of the sources rang es between 1.5 and 25 x 10(-14) erg cm(-2) s(-1), the lower value being 3 t imes fainter than in previous BeppoSAX and ASCA surveys. Their R band magni tudes are in the range 12.8-22. Six of the Chandra sources are broad line q uasars with redshifts between 0.42 and 1.19, while the optical identificati on of the remaining four is quite varied: two are X-ray obscured, emission line AGN at z = 0.272 and z = 0.683, one is a starburst galaxy at z = 0.016 and one, most unusually, is an apparently normal galaxy at z = 0.158. Thes e findings confirm and extend down to fainter X-ray fluxes the BeppoSAX res ults, in providing samples with a wide range of X-ray and optical propertie s. The ratio between the soft X-ray and the optical luminosity of the z = 0 .158 galaxy is a factor at least 30 higher than that of normal galaxies, an d similar to those of AGN. The high X-ray luminosity and the lack of optica l emission lines suggest an AGN in which either continuum beaming dominates , or emission lines are obscured or not efficiently produced. (C) 2000 Else vier Science B.V. All rights reserved.