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1 Introduction

The REX survey is an effort aimed at the selection of a sizable, statistically complete sample of Radio-Emitting X-ray sources (REXs). A detailed description of this survey has been presented in Caccianiga et al. (1999). In summary, the REX survey is the result of a positional cross-correlation between the NRAO VLA Sky Survey (NVSS, Condon et al. 1998) at 1.4 GHz and an X-ray catalog of about 17 000 serendipitous sources detected in 1202 pointed ROSAT PSPC fields. The flux density limit in the radio band (at 1.4 GHz) is 5 mJy while in the X-ray band the flux limits range from $\sim$3.5$\ $10-14 erg s-1 cm-2 to $\sim$2$\ $10-13 erg s-1 cm-2 (0.5-2.0 keV). The area covered at the highest flux limit is about 2200 deg2. The cross-correlation has produced a catalog of $\sim$1600 REX sources. The spectroscopic observation of the REXs is in progress and, to date, the percentage of identifications is about 30%. Among these sources, 232 Emission Line (EL) objects (mostly AGNs), 72 BL Lacs and 176 optically "non-active'' galaxies have been found. About 30% of these objects are newly discovered. A previous paper (Wolter et al. 1998) reported a small fraction of these new identifications; in this paper we present the spectra of 71 EL objects not included in Wolter et al. (1998). In addition, we present other 19 EL objects that were included in a preliminary version of the REX survey but not in the final catalog.

The paper is organized as follows: in Sect. 2 we present the optical observations, in Sect. 3 we explain the criteria used for the classification of the EL sources, in Sect. 4 we discuss the general radio and X-ray properties of the EL AGNs discovered so far in the REX survey. Our conclusions are summarized in Sect. 5. Throughout this paper we use H0=50 km s-1 Mpc-1 and q0=0.


  \begin{figure}{ \psfig{figure=h1886a1.eps,width=18cm} }\end{figure} Figure 1: Optical spectra of the 71 EL AGNs included in the REX survey


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  \begin{figure}{ \psfig{figure=h1886a13.eps,width=18cm} }\end{figure} Figure 2: Optical spectra of the 19 EL AGN not included in the REX survey


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