I am an assistant professor in computational and theoretical astrophysics
at the Anton Pannekoek Institute of the University of Amsterdam and
the PI of the NWO-Vidi project TRI-Waves* on the evolution of triple-star systems
towards gravitational wave sources. I'm also a member of GRAPPA and a chair of
the LISA working package on stellar-mass sources.

* PhD and PD positions available to start in 2022!

I'm interested in the formation and evolution of stellar systems, such as binaries and triples.
How do they evolve? And how do they end their lives? What are the properties of the
energetic and transient phenomena they produce - both in electromagnetic and in
gravitational wave radiation?


Contact details

toonen [at] uva.nl
s.toonen [at] bham.ac.uk will be deactivated soon

Science Park 904
1098 XH Amsterdam
The Netherlands


Recent highlights

sequential merger

Sequentail mergers in triples

We present a proof-of-concept on how massive stellar triples can lead to sequential binary black hole mergers and GW emission observable by current-day GW facilities. We outline their formation, and explore these events in the context the pair-instability gap. We find that binary black-hole mergers in the pair-instability mass gap can be of triple origin and therefore are not exclusively formed in dense dynamical environments. We propose that the progenitor of GW170729 is a low-metallicity field triple. We support the premise that GW190521 could not have been formed in the field.


Searching for detached black holes

Stellar-mass black holes are typically discovered in compact interacting systems; either through accretion or mergers. HR6819 could harbor one of the first black holes in a detached system, shedding light on wider systems for the first times. If so, it would be the nearest black hole and part of a triple system nonetheless! In this paper we lay out theoretical reasons why the latter is not likely in the case of HR6819.

Tertiary mass transfer

Tertiary mass transfer

In this paper, we consider triple systems in which the inner binary is driven to merger due to mass accretion from the tertiary star via a circumbinary disk. Using analytic- and population synthesis-based calculations performed, we find that this scenario is quite common! Moreover, the scenario broadly predicts mergers of near equal-mass binaries, producing blue stragglers (BSs), Type Ia supernovae, gamma-ray bursts and gravitational wave-induced mergers, along with the presence of an outer WD tertiary companion. The mechanism considered here could produce hypervelocity MS stars, WDs, and even millisecond pulsars with masses close to the Chandrasekhar mass limit, and be used to constrain the maximum remnant masses at the time of any supernova explosion.

Check it out

Download TRES & SeBa from GitHub

to simulate the evolution of stellar triples and binaries

Our webtool

What's the dynamical impact of the tertiary in your favorite triple?

Join our Facebook group

on triple evolution and dynamics

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