Hi there. I am a PhD student at the Radboud University in Nijmegen, the Netherlands, working in the field of astrophysics under supervision of Gijs Nelemans and Onno Pols.

My focus is on the evolution of massive stars, particularly those in binary systems, and my research is computational in nature. I study the evolution of massive stars and binaries through a combination of detailed stellar-evolution computations (including models of stellar interiors) and rapid population-synthesis calculations that allow to model milions of stars.

I am particularly interested in the formation of gravitational-wave sources: binary black-hole and neutron-star mergers detected by the LIGO and Virgo interferometers.
But my interests include various aspects of stellar and binary evolution, stellar interiors and chemical mixing, mass transfer and common-envelope evolution, compact objects and X-ray binaries, as well as dynamical interactions in dense stellar clusters.
You can learn more about my work here. For the recent highlights see below.

Apart from stars and all that, I love mountains, cuisine-traveling, playing squash (until I can move no more) and chess. Take care!

It has to be cool: on supergiant progenitors of binary BH mergers from CE evolution

June 2020

Common-envelope (CE) evolution in isolated binary systems is thought to be one of the leading channels for producing double compact object systems (binaries of black holes, BH, or neutron stars, NS) that eventually merge and can be detected in gravitational waves. The CE phase itself, during which a BH or a NS spirals in inside a supergiant's envelope, is one of the most uncertain stages of the channel. In this paper we ask a question which BH binaries with supergiant companions will evolve through and can potentially survive the CE phase.
In pursue of the most optimistic case, we make a number of physically extreme assumptions in favor of easier CE ejection. We find that even then a successful CE evolution in BH binaries is only possible if the stellar companion is a convective-envelope star: a red supergiant (RSG) as shown in the HR diagram below.

Interestingly, no RSGs are observed above luminosities of about log(L/L) ≈ 5.6−5.8, corresponding to stars with initial above 40 solar masses. Either such RSGs elude detection due to short lifetimes, or they do not exist (for instance due to strong winds), implying an upper limit on the masses of binary BH mergers from CE evolution at about 50 M⊙.

Jakub Klencki, Gijs Nelemans, Alina G. Istrate, Martyna Chruslinska
Astronomy & Astrophysics (accepted 27/09)
arXiv: 2006.11286 [astro-ph.SR]
Jakub Klencki

Institute for Mathematics, Astrophysics and Particle Physics
Radboud University

Heyendaalseweg 135
6525 AJ Nijmegen, NL