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[26.02] Studying the soft X--ray properties of the hard X--ray---selected HELLAS sources

C. Vignali (Dipartimento di Astronomia di Bologna-Osservatorio Astronomico di Bologna), A. Comastri (Osservatorio Astronomico di Bologna), F. Fiore (Osservatorio Astronomico di Roma)

We present the ROSAT X-ray properties of the hard X-ray---selected sources discovered by the High-Energy LLarge Area Survey (HELLAS) with BeppoSAX. Though the soft X-ray spectrum of the sources is generally well described by a steep (\Gamma~q2.3) power law continuum, nevertheless the hardness ratio analysis seems to indicate a large variety of soft X-ray properties, as well as the presence of a certain number of hard objects, including Type~1s. These findings extend to lower energies the results obtained with the BeppoSAX analysis. The comparison of the hardness ratio results with those derived from the ROSAT Deep Survey indicates the likely presence of a larger number of absorbed objects in the HELLAS survey, in agreement with expectations.

This work is supported by the MURST grant Cofin 98-02-32 and by the ASI contract ASI-ARS-99-75.