My main research interest is to test general relativity by modeling and interpreting relativistic reflection features from black holes. These features originate from the reflection of primary X-ray photons at the innermost parts of the accretion disk. Due to the intermediate proximity to the black hole, the photon trajectories and energies are heavily influenced by strong gravity effects, leading to a distortion of the reflection features. Properly modeling this distortion does allow us to draw conclusions about parameters of the black hole system like the accretion geometry, the inclination to the system, or spin of the the black hole. Besides developing such models, I also put great effort in applying these to recent observations of galactic black holes (such as Cygnus X-1) or AGN (1H0707-495}. For this purpose, simultaneous data of XMM-Newton, RXTE, and Chandra were used. Besides specializing on relativistic reflection, I am also involved in multi-wavelength observations of black holes in order to better understand the greater picture of the connection between the jet and the accretion disk. Moreover, the ray tracing techniques developed for black holes can be applied to neutron star spectra. Properly modeling the time resolved spectra and pulse profiles relativistically will give us insights in the accretion geometry as well as providing us with mass and radius constraints.
In the following the models for relativstic reflection are provided
The RELLINE Model
I created a model called RELLINE for fitting X-ray data with programs like XSPEC or ISIS. It models relativistically broadened emission lines from accreting systems. Moreover I added the implementation RELCONV, which is a convolution model and calculates the relativistic smearing of the whole spectrum.
The RELXILL Model
The RELXILL model is joins the reflection code XILLVER with the RELCONV model. With this approach the angular resolved reflection is properly connected to the relativstic smearing kernel.