News aus der Fakultät
07.05.2025
Erfolgreiche Verteidigung der Dissertation von Xiaohang Dai
Successful Doctoral Defense by Ms Xiaohang Dai
Ms Xiaohang Dai successfully defended her doctoral thesis on May 5, 2025. We extend our warmest congratulations to her on this significant academic achievement.
Ms Dai conducted her research in the High-Energy Astrophysics section at the Institute for Astronomy and Astrophysics Tübingen (IAAT). Her work was supported by the Chinese Scholarship Council and the University of Tübingen.
Dai's comprehensive investigation into some of the most powerful high-energy sources in the universe—X-ray binaries—has unveiled fresh insights into the behavior of neutron stars and black holes as they accrete matter from companion stars. The research, based on data from several space observatories including eROSITA, NICER, NuSTAR, XMM-Newton, and Insight-HXMT, highlights how these exotic systems serve as natural laboratories for studying strong gravity, magnetic fields, and relativistic phenomena.
The study focuses in particular on the spectral and timing properties of black hole and neutron star X-ray binaries, with detailed analyses of two notable black hole systems: MAXI J1348−630 and GRS 1915+105. Observations of MAXI J1348−630 uncovered a critical luminosity threshold that marks a shift in accretion behavior, while quasi-periodic oscillations and state transitions offered new insights into how matter interacts near the event horizon. In the case of GRS 1915+105, combined NICER and NuSTAR data enabled the first joint analysis of quasi-periodic oscillations and disk winds, offering a possible explanation for the system’s unusual rebrightening episodes.
The research also contributes to the search for previously undetected black hole candidates, using eROSITA survey data to identify faint and quiescent systems that may have eluded earlier detection.
On the neutron star side, the study tracks the spin evolution and irregularities in magnetized accretors. For SXP 726, a Be/X-ray binary in the Small Magellanic Cloud, coordinated observations show clear spin-up trends indicative of active accretion. Meanwhile, the ultraluminous X-ray pulsar Swift J0243.6+6124 revealed rare anti-glitch and glitch-like timing features, potentially offering clues about the internal and magnetospheric dynamics of neutron stars.
We commend her dedication and contributions to the field and wish her continued success in her future scientific endeavors.
Picture: Ms, now Dr. Dai, together with Prof. Andrea Santangelo, main supervisor of the doctoral research.