The so-called Magnificent Seven neutron stars like RXJ1856.5-3754 and RXJ0720.4-3125 are of particular interest, because one can observe directly the surface and, hence, one can in principle determine mass, radius, and spin, in order to constrain the equation-of-state.

We investigate isolated neuron stars such as the Magnificent Seven in various ways: X-ray spectroscopy, proper motion by deep optical and X-ray imaging, deep radio observations.

We also search for more such radio-quiet neutron stars, which can be found by their large X-ray to optical flux ratio with soft X-ray and blue optical emission: We use deep X-ray pointings from ROSAT and XMM and perform deep optical follow-up observations of unidentified soft sources. In addition, we also use deep optical pointings of large telescopes, found in public archives, to search for very faint objects, which are blue and/or fast moving.

Furthermore, we model the neutron star population of the Galactic disk and the Gould Belt, using cooling curves and a 3D absorption model.

We also consider the relevance of such neutron stars to gravitational wave astronomy regarding both the equation of state and the emission of gravitational waves.

We participate in the SFB / TR 7 "Gravitational Wave Astronomy" with one project on neutron stars. We closely collaborate with G. Hasinger, F. Haberl, J. Trümper (MPE Garching), K. Werner (Uni Tübingen), as well as S. Popov (Sternberg, Moskau) and B. Posselt (CFA Harvard).