Karl Forster — Page 6

arXiv1997

Evidence for Relativistic Outflows in Narrow-line Seyfert 1 Galaxies

We report the observation of features near 1 keV in the ASCA spectra from three ``Narrow Line Seyfert 1'' (NLS1) galaxies. We interpret these as oxygen absorption in a highly relativistic outflow. If interpreted as absorption edges, the implied velocities are 0.2--0.3c, near the limit predicted by ``line-locking'' radiative acceleration. If instead interpreted as broad absorption lines, the implied velocities are ~0.57c, interestingly near the velocity of particles in the last stable orbit around a Kerr black hole, although a physical interpretation of this is not obvious. The features are reminiscent of the UV absorption lines seen in broad absorption line quasars (BALQSOs), but with larger velocities, and we note the remarkable similarities in the optical emission line and broad band properties of NLS1s and low-ionization BALQSOs.

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arXiv1996

Extreme X-ray Variability In The Narrow-Line QSO PHL 1092

A ROSAT observation of the narrow-line Fe II QSO PHL 1092 shows rapid variability that requires an efficiency of at least 0.13, exceeding the theoretical maximum for an accretion disk around a non-rotating black hole. Plausible explanations for this high efficiency incorporate anisotropic emission and/or accretion onto a rapidly rotating black hole, the latter recently suggested by Kwan et al. as a mechanism for generating PHL 1092's strong Fe II lines by mechanical heating in an accretion disk. The soft X-ray luminosity of PHL 1092 had also increased by a factor of 21 over the weak Einstein detection, to more than 5 x 10^46 ergs/s. Its photon spectral index of 4.2 is among the steepest of any AGN. These X-ray properties are characteristic of narrow-line Seyfert 1 galaxies, of which PHL 1092 is evidently a very luminous member. Narrow-line QSOs also extend a significant correlation between X-ray luminosity and X-ray spectral index which we have found among a large sample of optically-selected, narrow-line Seyfert 1 galaxies observed by ROSAT.

astro-ph↗