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Ultrasoft narrow‐line Seyfert 1 galaxies and X‐ray surveys
Author(s) -
Brandt N.,
Boller T.
Publication year - 1998
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/asna.2123190104
Subject(s) - rosat , galaxy , physics , astrophysics , line (geometry) , spectral line , active galactic nucleus , spectral properties , astronomy , geometry , mathematics
We describe how recent X‐ray surveys have led to advances in the understanding of ultrasoft narrow‐line Seyfert 1 galaxies. The number of known ultrasoft narrow‐line Seyfert 1s has increased greatly in recent years due to X‐ray surveys, and it is now possible to obtain high quality 0.1–10 keV spectral and variability measurements for a large number of these galaxies. We generalize some of the correlations between X‐ray properties and optical emission line properties, focusing on how the ROSAT band spectral slope appears to be directly connected to the Boroson & Green (1992) primary eigenvector. We discuss how ultrasoft narrow‐line Seyfert 1s may well have extremal values of a primary physical parameter, and we describe new projects that should further improve our understanding of these extreme representatives of Seyfert activity.