LOFT: a large observatory for x-ray timing

The X-ray sky in high time resolution holds the key to a number of observables related to fundamental physics, inaccessible to other types of investigations, such as imaging, spectroscopy and polarimetry. Strong gravity effects, the measurement of the mass of black holes and neutron stars, the equation of state of ultradense matter are among the objectives of such observations. The prospects for future, non-focused X-ray timing experiments after the exciting age of RXTE/PCA are very uncertain, mostly due to the technological limitations that need to be faced to realize experiments with effective areas in the range of several square meters, meeting the scientific requirements. We are developing large-area monolithic Silicon drift detectors offering high time and energy resolution at room temperature, with modest resources and operation complexity (e.g., read-out) per unit area. Based on the properties of the detector and read-out electronics we measured in laboratory, we built a concept for a realistic unprecedented large mission devoted to X-ray timing in the energy range 2-30 keV. We show that effective areas in the range of 10-15 square meters are within reach, by using a conventional spacecraft platform and launcher.