Data: 12.03.2024

Aleksandra Olejak (MPIA, Garching)

Fingerprints of binary star interactions in the parameters of binary black hole mergers

Streszczenie:
The growing database of gravitational wave (GW) detections with inferred parameters of merging black holes (BH-BH) contains non-obvious insights into their formation scenarios. Interactions in massive star binaries in the form of stable or unstable mass transfer are expected to accompany the formation of GW sources. Those interactions could leave characteristic fingerprints in the parameters (masses and spins) of detected BH-BH systems. Therefore, their identification would help in constraining poorly understood parts of stellar evolution. Restricted criteria for common envelope development (i.e. unstable mass transfer) combined with efficient tidal spin-up of stripped helium core may result in a characteristic pattern in effective spin vs mass ratio distributions of merging BH-BH, consistent with GW detections. In particular, the progenitors of unequal BH-BH systems in the stable mass transfer formation scenario experience more efficient orbital contraction during the second Roche Lobe Overflow than nearly equal mass component systems. That makes it easier for unequal-mass progenitors to enter the tidal spin-up regime and later merge due to GW emission. Our result is, however, sensitive to highly uncertain assumptions on angular momentum loss. We conclude that a significant fraction of unequal-mass BH-BH mergers among the future GW detections could indicate the contribution of a stable mass transfer formation channel. Such a population would be consistent with the mass ratio reversal scenario during the first, relatively conservative mass transfer, and low angular momentum loss during the second, highly non-conservative mass transfer phase.

Bio:
- engineer at the Faculty of Physics, Warsaw University of Technology (2017)
- Master's degree at Astronomical Observatory, UW (2019)
- PhD at CAMK PAN (2023)
- currently a postdoc fellow at the Max Planck Institute for Astrophysics in Garching
Main scientific interests:
evolution of massive stars in isolated binary systems,formation scenarios of binary black hole mergers, gravitational wave sources and their origin (mainly under LIGO/Virgo and LISA