caa a22 4500 469077379 CHVBK 20180323132938.0 cr unu---uuuuu 170328e19920901xx s 000 0 eng 10.1007/BF02507855 doi (NATIONALLICENCE)springer-10.1007/BF02507855 X-ray spectral signatures of very thick cold matter in the Spectra of seyfert galaxies [Elektronische Daten] [L. Piro, M. Yamauchi, M. Matsuoka] Summary: Over the last few years, GINGA observations of several bright Seyfert galaxies have revealed the existence of a new flat component in the X-ray spectrum of these objects above 8 keV. This component (the <<high-energy bump>>) is probably produced by the reprocessing of the intrinsic emission (through Compton scattering and photoelectric absorption) by a very thick and cold medium in the environment of the central source, such as an accretion disk. An alternative explanation is provided by partial covering and reprocessing by thick clouds, whose existence is supported by the latest results on the broad line region obtained by line reverberation measurements in the optical-ultraviolet band. The presence of iron fluorescent lines at 6.4 keV with an equivalent width ≅ (100÷200) eV in all those galaxies supports both scenarios. The implications of the presence of the high-energy bump on the spectral shape of the intrinsic continuum, the level of the soft X-ray excess and the X-ray background are briefly pointed out. Società Italiana di Fisica, 1992 X-ray sources nationallicence Piro L. Istituto di Astrofisica Spaziale, CNR, Via E. Fermi 21, 00044, Frascati, Italia aut Yamauchi M. The Institute of Physical and Chemical Research, 351-01, Wako-shi, Saitama, Japan aut Matsuoka M. The Institute of Physical and Chemical Research, 351-01, Wako-shi, Saitama, Japan aut Il Nuovo Cimento C Kluwer Academic Publishers 15/5(1992-09-01), 811-818 0390-5551 15:5<811 1992 15 11543 https://doi.org/10.1007/BF02507855 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF02507855 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Piro L. Istituto di Astrofisica Spaziale, CNR, Via E. Fermi 21, 00044, Frascati, Italia aut NATIONALLICENCE 700 1- Yamauchi M. The Institute of Physical and Chemical Research, 351-01, Wako-shi, Saitama, Japan aut NATIONALLICENCE 700 1- Matsuoka M. The Institute of Physical and Chemical Research, 351-01, Wako-shi, Saitama, Japan aut NATIONALLICENCE 773 0- Il Nuovo Cimento C Kluwer Academic Publishers 15/5(1992-09-01), 811-818 0390-5551 15:5<811 1992 15 11543 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer