Premium
Black holes in AGN: recent results on IC 4329a and NGC 4945
Author(s) -
Madejski G.,
Done Ch.,
Zycki P.
Publication year - 1999
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/1521-3994(199908)320:4/5<240::aid-asna240>3.0.co;2-f
Subject(s) - physics , astrophysics , active galactic nucleus , galaxy , line (geometry) , black hole (networking) , radiative transfer , doubly ionized oxygen , emission spectrum , spectral line , astronomy , optics , geometry , computer network , routing protocol , mathematics , routing (electronic design automation) , computer science , link state routing protocol
This paper briefly reviews the observations which provide the best evidence for the presence of black holes in active galaxies: kinematic studies using optical emission lines as well as the distribution of megamaser spots; X–ray variability; and the profile of the Fe Kα X–ray emission line. It summarizes the current popular models for the radiative processes operating in radio‐quiet AGN. Finally, it presents two recent X–ray observations of AGN, where (1) the shape of the Fe K line indicates a diversity of locations where such lines originate (based on the ASCA & RXTE data for IC 4329a and NGC 5548), and (2) the rapid hard X–ray variability measured with the RXTE in the heavily absorbed Seyfert NGC 4945 implies that the Thomson‐thick absorber surrounding the nucleus (with τ ≅ 2.4) is unlikely to subtend a large solid angle to the nucleus, meaning that it is not geometrically thick, but is confined to a rather thin, disk‐like structure.