THE BeppoSAX DEEP SURVEYS

We present the preliminary results of a survey that makes use of several deep exposures obtained with the X-Ray telescopes of the BeppoSAX satellite. The survey limiting sensitivity is 5× 10 erg cmsin the 2-10 keV band and 7 × 10 erg cmsin the harder 5-10 keV band. We find that the 2-10 keV LogN-LogS is consistent with that determined in ASCA surveys. The counts in the 5-10 keV band imply either a very hard average spectral slope or the existence of a population of heavily absorbed sources that can hardly be detected in soft X-ray surveys. A sample of 83 serendipitous sources has been compiled from a systematic search in 50 MECS images. The analysis of the hardness ratio of this sample also implies very hard or heavily cutoff spectral shapes.