X-rays are emitted due to energetic processes, either high temperatures (for example thermal emission) or through populations of highly accelerated particles (for example Bremsstrahlung radiation, Compton scattering, etc). Many celestial bodies emit in the X-ray, notably stars, compact objects (neutron stars, white dwarfs), accretion around compact objects including black holes, but also the remains of stars (supernova remnants), galaxy clusters, and even aurora on other planets and charge exchange. Compact objects, due to their small size, accretion discs and stars are highly variable and therefore many transient events have X-ray counterparts and many multi-messenger events are highly energetic and therefore also emit in the X-ray.

The X-ray Centre of Expertise proposes assistance in learning to reduce and analyse X-ray data from the full array of X-ray observatories and instruments, how to use various X-ray packages available, and also provides assistance in X-ray models, proposal writing and exploiting the large volumes of data, notably through the various catalogues available and the study of populations. Specific expertise is also available for the study of transients and multi-wavelength studies of X-ray sources.

• Expert support on writing observing proposals for different facilities
• Support for X-ray data reduction/analysis for all X-ray observatories (see above)
• Data reduction of photometric and spectroscopic data (detailed knowledge of high resolution X-ray spectroscopy) with a specialisation in astrophysical transients
• Interpretation/modeling of photometric and spectroscopic emission of astrophysical transients
• Specialised knowledge on the REFLEX model for the active Galactic Nuclei emission and the JETSET model for electromagnetic emission of astrophysical jets.
• Spectroscopic classification of astrophysical transients
• Theoretical studies on nucleosynthesis of r-process
• Population studies, rates and statistics of astrophysical transients
• Data mining the archives and catalogue usage