Publications
How much hydrogen is in Type Ib and IIb supernova progenitors?
​This study analyzed in detail all the progenitors of hydrogen-deficient supernovae identified in pre-supernova images in one coherent framework, as opposed to individual studies of each progenitor using different methods. The study addressed the limits in determining the progenitor properties associated with the uncertainty in distance and dust extinction, using a combination of detailed binary stellar evolution simulations and stellar atmospheres that were converted to synthetic photometry. The main conclusion of the study is that progenitors of apparently hydrogen-free supernovae (Type Ib) are likely to still contain non-negligible amounts of hydrogen, that are nevertheless not observed in the spectra of these supernovae.
The excess of cool supergiants from contemporary stellar evolution models defies the metallicity-independent Humphreys-Davidson limit
This study quantitatively compared the predictions from modern stellar evolution simulations with catalogues of cool super-giant stars in the Magellanic Clouds by utilizing a population synthesis approach based on a large set of detailed stellar evolution simulations. The study shows that the empirical Humphreys-Davidson limit – the absence of cool supergiant stars above a luminosity threshold – is difficult to reconcile with theory, with theory predicting the existence of stars that are not found in nature. This discrepancy can be alleviated, as the study show, by increasing the extent of mixing between the stellar core and envelope beyond commonly-used assumptions.
Effects of winds on the leftover hydrogen in massive stars following Roche lobe overflow
This study of interacting massive binary stars with two distinct wind mass-loss rate recipes shows that stars losing most of their envelope through Roche-lobe overflow can still retain a significant mass of hydrogen, emphasizing that the common assumption that binary interaction removes the stellar envelope is wrong, and the post-interaction stellar wind is another crucial ingredient in determining the final fate of massive stars.
Asymmetric core collapse of rapidly rotating massive star
This study of the asymmetric core collapse of rapidly rotating massive stars demonstrates with sophisticated hydrodynamic simulations the importance of the core rotation rate at the evolutionary endpoint of massive stars. I showed that fast core rotation can lead to energetic stellar explosions and to the formation of neutron-rich material in thick discs around the collapsing core, and quantified the rotation rate for these aforementioned effects. This study suggests that rapidly rotating stellar cores at the terminal collapse can contribute to rare energetic supernovae and to the production of heavy neutron-rich elements.