An artist's impression of an X-ray binary Zoom Image
An artist's impression of an X-ray binary

High Energy Astrophysics

X-ray Binaries and Stellar Compact Objects

The group studies the properties of X-ray binaries, as well as neutron stars and white dwarfs. We investigate properties of individual objects - such as the X-ray flux/luminosity, timing and spectral behaviour - as well as global properties of populations of these compact objects with respect to their host galaxies.

Marat Gilfanov studies X-ray binaries, accretion and spectral formation in the vicinity of compact objects, ultra-luminous X-ray sources, etc. He also works on populations of accreting neutron stars and stellar mass black holes in external galaxies in relation to characteristics of their hosts, such as star-formaiton activity, metallicity etc. In addition, Marat also investigates the nature of progenitors of type Ia supernovae using various electro-magnetic signatures of their pre-supernova evolution and their impact on the environment.

Filippos Koliopanos studies X-ray binaries, especially the subset known as Ultra Compact X-ray Binaries, which have orbital periods of less than one hour. Because their short periods do not allow for a hydrogen rich, main-sequence donor, we expect the chemical composition of the accreting material to be vastly different from that of solar-type stars. Filippos is working to understand the impact of different elemental abundances of the accretion disk on the spectrum of the reflected photons.

Mikkel Nielsen studies the nature of the progenitors of type Ia supernovae and related fields such as supersoft X-ray emission from steady-accreting white dwarfs and symbiotic binaries, and the interaction of soft X-rays with circumbinary and interstellar matter.

Tyrone Woods is investigating the nature of Type Ia supernova progenitors. In particular, he is developing new means to test the viability of supersoft X-ray sources (stably-accreting white dwarfs) as likely progenitors. Tyrone is also interested in the general problem of binary stellar evolution, in particular mass transfer in X-ray binaries, and the physics of the common envelope phase.

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