Astronomy and Astrophysics – Astrophysics
Scientific paper
Feb 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996rftu.proc..425b&link_type=abstract
International Conference on X-ray Astronomy and Astrophysics: Röntgenstrahlung from the Universe, p. 425 - 426
Astronomy and Astrophysics
Astrophysics
Seyfert Galaxies: Active Galactic Nuclei, Seyfert Galaxies: X Rays, Seyfert Galaxies: Black Holes
Scientific paper
The authors report on AGN with extremely soft X-ray spectra observed with ROSAT. From their optical emission lines these objects are classified as narrow-line Seyfert 1 galaxies (NLS1), almost all with extremely large Fe II/Hβ ratios and relatively narrow optical lines of hydrogen. It is found that NLS1 have generally steeper soft X-ray continuum slopes than normal Seyfert 1s, and there may exist an anticorrelation between 0.1-2.4 keV continuum slope and the FWHM of the Hβ line. Objects with steep 0.1-2.4 keV continuum slopes and Hβ FWHM > 3000 km s-1 are clearly discriminated against by nature. When simple power-law models are fit to the data, photon indices reach values up to about 5, much higher than is usually seen in Seyfert 1s. The authors consider models for NLS1 where they are Seyfert 1s with extremal value black hole mass and/or accretion rate, of pole-on orientation and warm absorption and confront these models with the known properties of NLS1. Models with smaller mass black holes and/or accretion rate show some promise.
Boller Th.
Brandt Wiliam N.
Fink Henner
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