Obscuring clouds playing hide-and-seek in the Active Nucleus H0557-385
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.
Cite
@article{arxiv.0810.0918,
title = {Obscuring clouds playing hide-and-seek in the Active Nucleus H0557-385},
author = {A. L. Longinotti and S. Bianchi and L. Ballo and I. de la Calle and M. Guainazzi},
journal= {arXiv preprint arXiv:0810.0918},
year = {2009}
}
Comments
5 pages, accepted for publication on MNRAS Letters