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arXiv · astro-ph/9512045

Ultrasoft transient X-ray emission from AGN

K. Mannheim·D. Grupe·K. Beuermann·H. -C. Thomas·H. H. Fink
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Abstract

We report some remarkable and unexpected results of optical/UV/X-ray follow-up observations of bright soft X-ray selected AGN from the ROSAT All-Sky-Survey. The majority of these AGN are rather anonymous Seyfert galaxies, mostly of the narrow-line Seyfert 1 subtype (nlSy1). We confirm the well-known X-ray variability by factors of a few. However, we also found strikingly different variability patterns: (i) a drop in the PSPC count rate by a factor of ~400 in WPVS007, (ii) a bolometrically dominant soft X-ray component decreasing in flux by a factor ~100 in IC 3599 accompanied by a decrease in optical emission line fluxes, and (iii) a drastic X-ray spectral change in RX J0134-42 from ultrasoft to a typical hard Seyfert spectrum. These dramatic variations occur within a (few) year(s), implying that the accretion flow in the immediate vicinity of the central black hole must have undergone a major change. We discuss possible physical explanations such as accretion disk instabilities or the tidal disruption of stars.

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K. Mannheim, D. Grupe, K. Beuermann, H. -C. Thomas, H. H. Fink. 1995-12-08. Ultrasoft transient X-ray emission from AGN. https://arxiv.org/abs/astro-ph/9512045

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