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arXiv · 0810.0918

Obscuring clouds playing hide-and-seek in the Active Nucleus H0557-385

A. L. Longinotti·S. Bianchi·L. Ballo·I. de la Calle·M. Guainazzi
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Abstract

This paper reports on two XMM-Newton observations of the Seyfert 1 Galaxy H0557-385 obtained in 2006, which show the source at an historical low flux state, more than a factor of 10 lower than a previous XMM-Newton look in 2002. The low flux spectrum presents a strong Fe Kalpha line associated to a Compton reflection continuum. An additional spectral line around 6.6 keV is required to fit Kalpha emission from Fe XXV. The spectral curvature below 6 keV implies obscuration by neutral gas with a column density of 8*10^{23}cm^{-2} partially covering the primary emission, which still contributes for a few percent of the soft X-ray emission. Absorption by ionised material on the line of sight is required to fit the deep trough below 1 keV. The comparison of the two spectral states shows that the flux transition is to be ascribed entirely to intervening line-of-sight clouds with high column density.

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A. L. Longinotti, S. Bianchi, L. Ballo, I. de la Calle, M. Guainazzi. 2008-10-06. Obscuring clouds playing hide-and-seek in the Active Nucleus H0557-385. https://doi.org/10.1111/j.1745-3933.2008.00571.x

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