X-ray Binary Stars
Cataclysmic Variables (CVs) are compact, short period, interacting binaries with a white dwarf as the primary star. We are interested lies in populations studies and on the detailed physical interaction scenarios between the two stars in the binary. We use spectral and temporal information from X-ray missions like XMM-Newton and eROSITA to uncover new systems and attempt an understanding of the physical mechanisms.
Isolated Neutron Stars
Isolated Neutron stars are a new class of soft X-ray emitters discovered by ROSAT. They show unique properties that attract a lot of follow-up studies over the last decades: a very soft, thermal X-ray spectrum with very little interstellar absorption, no obvious sign of magnetospheric emission, and no association with a supernova remnant. Despite the expection to find thousands of those objects in the ROSAT all-sky survey, to date only seven could be uniquely identified, now termed the Magnificent Seven. The great interest in those sources arose from the fact, that these stars offer the unique opportunity to study a neutron's star surface uncontaminated from any other emission. There is hope, that those stars help to derive constraints on the equation-of-state of ultradense matter. Several projects with eROSITA are underway to study those objects.
We are deeply involved in the design and scientific exploitation of the eROSITA all-sky surveys. eROSITA is the main instrument on SRG (Spektrum-Roentgen-Gamma), which was launched in July 2019. In December 2019 the first of planned 8 all-sky surveys was started that will outperform all past X-ray surveys and allow comprehensive populations of all kinds of galactic and extragalactic X-.ray emitters to establish.