09.05.2025

Erfolgreiche Verteidigung der Dissertation von Artur Avakyan

Mr Artur Avakyan successfully defended his doctoral thesis on May 7, 2025. We extend our warmest congratulations to him on this significant academic achievement.

Mr Avakyan conducted his research in the High-Energy Astrophysics section at the Institute for Astronomy and Astrophysics Tübingen (IAAT), in the framework of the eROSTEP 
(The eROSITA View of Stellar Endpoints) program,  a research unit coordinated between the core institutes of the German eROSITA consortium and supported by the Deutsche Forschungsgemeinschaft (DFG).

Mr. Avakyan focused on studies of Galactic X-ray Binaries in the era of eROSITA and Beyond.

As a first part of his work he compiled, with Mr. Marvin Neumann, two up-to-date catalogues of Galactic low-mass and high-mass X-ray binaries, increasing the known sample by ~70% through careful mining of X-ray, optical, and infrared archives.

He then studied the first eROSITA all-sky data release to develop and apply a supervised machine-learning pipeline, uncovering 192 new XRB candidates and carrying out XMM-Newton follow-up observations on two of them—ultimately identifying them as a chromospherically active subgiant and a novalike cataclysmic variable rather than true XRBs. In addition, moving from observational work to a more theoretical study, Mr. Avakyan extended the open code ‘Freddi' to include a thermal-wind model and used it to simulate the 2002 outburst of 4U 1543–47, demonstrating that neglecting thermal winds leads to a ~1.6× overestimate of the viscous parameter α.

Together, these efforts establish a richer census of Galactic XRBs, showcase the potential and current limitations of eROSITA for discovering new systems, and advance numerical tools for probing accretion-disc physics.
Mr. Avakyan will continue his work at the IAAT as a postdoc.

We commend his dedication and contributions to the field and wish him continued success in his future scientific endeavors.

Five articles emerged from Dr. Avakyan’s work:

"XRBcats: Galactic Low-Mass X-ray binary catalogue"
Avakyan A., Neumann M., Zainab A., Doroshenko V., Wilms J., Santangelo A.,
2023, A&A, 675, A199

"XRBcats: Galactic High Mass X-ray Binary Catalogue"
Neumann M., Avakyan A., Doroshenko V., & Santangelo A., 2023, A&A, 677,
A134

"Hunting down new Galactic XRBs in eROSITA-DE DR1 using ML"
Avakyan A., Zainab A., Doroshenko V., Wilms J., Salvato M., Schwope A.,
Santangelo A., (2025, ready for submission)

"XMM-Newton follow-up of two eROSITA X-ray binary candidates"
Avakyan A., Zainab A., Doroshenko V., Wilms J., Schwope A., Buckley D.,
Brink J., Santangelo A., (2025, under review)

"The effect of thermal winds on the outbursts evolution of LMXB systems"
Avakyan A., Lipunova G., & Malanchev K., 2024, MNRAS, 527, 3709