Matthias Ehle

Impacts on the IXO Observing Efficiency

The International X-ray Observatory (IXO) has a top level requirement that the observing efficiency be 85%. This is a challenging requirement, given that the observing efficiencies for CXO and XMM-Newton are between 60% and 70%. However, the L2 orbit for IXO means that it will not be subject to the earth block/radiation zone effects that are seen for CXO and XMM-Newton. Outside of these effects the efficiencies for CXO and XMM-Newton do approach 85%, so this requirement appears achievable for IXO. In this paper we itemize the effects which impact the observing efficiency, in order to guide the design of the observatory. Meeting the 85% requirement should be possible but will require careful attention to detail.

The Starburst Seyfert 2 Nucleus of NGC 1808 as Seen by XMM-Newton

NGC 1808 harbours an important star-forming activity in the central 20, triggered by an interaction with its companion NGC 1792, Dahlem et al. (1990, A&A, 240, 237). There are convincing arguments for and against the presence of a low luminosity AGN, Veron-Cetty & Veron (1985, A&A, 145, 425), Siebenmorgen et al. (2001, A&A, 377, 735), Junkes et al. (1995, A&A, 294, 8). The preliminary analysis of XMM-Newton data presented here sheds new light on the nature of the nuclear activity of the galaxy.