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A new population of soft X-ray weak quasars

G. Risaliti·A. Marconi·R. Maiolino·M. Salvati·P. Severgnini
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Abstract

Quasars selected in optical surveys by means of their blue or UV excess are known to be strong emitters in the X-rays, except for Broad Absorption Line (BAL) objects. In this paper we study the X-ray emission of quasars selected through their emission line spectrum rather than their blue excess. X-ray data are obtained by cross-correlating two optical samples (the Hamburg Survey Catalogue and the Palomar Transit Catalogue) with the WGA catalogue of ROSAT observations. We find that a significant fraction of objects are strongly underluminous in the X-rays. We discuss the physical nature of these sources and we propose an interpretation for their optical and X-ray properties based on a dust-poor and gas-rich absorber. Our results suggest the existence of a population of AGNs having a type 1 optical spectrum and a type 2 X-ray emission

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G. Risaliti, A. Marconi, R. Maiolino, M. Salvati, P. Severgnini. 2001-02-24. A new population of soft X-ray weak quasars. https://doi.org/10.1051/0004-6361%3A20010276

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