%0 Journal Article
%T Broad absorption features in wind-dominated ULXs?
%A Matthew J. Middleton
%A Dominic J. Walton
%A Timothy P. Roberts
%A Lucy Heil
%J Physics
%D 2013
%I arXiv
%R 10.1093/mnrasl/slt157
%X The luminosities of ultraluminous X-ray sources (ULXs) require an exotic solution with either super-critical accretion modes onto stellar mass black holes or sub-critical accretion onto intermediate mass black holes (IMBHs) being invoked. Discriminating between the two is non-trivial due to the present lack of a direct mass measurement. A key expectation of the super-critical mode of accretion is the presence of powerful radiatively-driven winds. Here we analyse XMM-Newton data from NGC 5408 X-1 and NGC 6946 X-1 and find that strong soft residuals present in the X-ray spectra can be reconciled with broadened, blue-shifted absorption by a partially ionised, optically thin phase of this wind. We derive initial values for the physical parameters of the wind; we also discuss other possible origins for the observed features.
%U http://arxiv.org/abs/1309.3134v2