NGC 7793 P13 is a variable (luminosity range ∼ 100) ultraluminous X-ray source (ULX) proposed to host a stellar-mass black hole of less than 15 M in a binary system with orbital period of 64 d and a 18-23 M B9Ia companion. Within the EXTraS project we discovered pulsations at a period of ∼0.42 s in two XMM-Newton observations of NGC 7793 P13, during which the source was detected at L X ∼ 2.1 × 10 39 and 5 × 10 39 erg s −1 (0.3-10 keV band). These findings unambiguously demonstrate that the compact object in NGC 7793 P13 is a neutron star accreting at super-Eddington rates. While standard accretion models face difficulties accounting for the pulsar X-ray luminosity, the presence of a multipolar magnetic field with B ∼ few × 10 13 G close to the base of the accretion column appears to be in agreement with the properties of the system.

As countries become increasingly urbanized, understanding how urban areas are changing within the landscape becomes increasingly important. Urbanized areas are the often

A general processing framework for urban road network extraction in high-resolution synthetic aperture radar images is proposed. It is based on novel multiscale detection of street candidates, followed by optimization using a Markov random field description of the road network. The latter step, in the path of recent technical literature, is enriched by the inclusion of a priori knowledge about road junctions and the automatic choice of most of the involved parameters. Advantages over existing and previous extraction and optimization procedures are proved by comparison using data from different sensors and locations.Index Terms-High-resolution synthetic aperture radar (SAR), Markov random fields (MRFs), road network, urban remote sensing.

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