The group welcomes Holly Preece, who recently obtained her PhD at the University of Cambridge and Armagh Observatory and Planetarium under supervision of Christopher Tout and Simon Jeffery.
New paper on a quadruple origin of GW190412
June 18 2020
In Hamers & Safarzadeh (2020; url), we investigate whether the gravitational wave source GW190412, consisting of two black holes with unusually unequal masses (mass ratio 0.28), could have formed from a "double merger" event in a hierarchical 3+1 quadruple system. In this scenario, the innermost binary merges first due to secular chaotic evolution. In the resulting triple, secular Lidov-Kozai evolution could subsequently lead to a second merger. We show that this scenario produces characteristics that are consistent with GW190412, although its likelihood is highly uncertain due to influences from stellar and binary evolution that were ignored here.
New paper on MS interactions in systems of the Multiple Star Catalogue
April 22 2020
In Hamers (2020; url), we study the long-term dynamical main-sequence (MS) evolution of hierarchical systems with 3 to 6 stars based on Andrei Tokovinin's Multiple Star Catalogue. We estimate statistical probabilities for strong interactions during the MS such as tidal evolution and mass transfer, and the onset of dynamical instability. Our results indicate that a significant fraction of high-multiplicity systems interact or become dynamically unstable already during the MS, with an increasing importance as the number of stars increases.
New paper on suborbital effects in multiple systems
April 20 2020
In Hamers (2020; url), we present an update to the SecularMultiple code, which integrates the long-term dynamical evolution of multiple systems with any number of bodies and hierarchical structure, provided that the system is composed of nested binaries. In the update, we incorporate hybrid integration techniques, allowing orbits to be either directly integrated (N-body method), or averaged over (secular method). We also implement orbit-averaging correction terms. The updated code is freely available on GitHub.
New paper on binary-binary scattering
March 9 2020
In Hamers & Samsing (2020; url), we study the gravitational effects of scattering of two binaries in the "weak" limit, i.e., in which the two binaries approach each other at a relatively large distance. We find that, to good approximation, one can use previous analytic results for binary-single scattering in the weak limit, and replace the mass of the single interloping body with the total mass of the interloping binary. In other words, the point mass approximation works well for weak binary-binary scattering.
New group member
March 1 2020
The group welcomes Patrick Neunteufel, previously a postdoc a the University of Leicester, and who completed his PhD with Norbert Langer at the Argelander Institute in Bonn in 2017.
New web site launched
October 23 2019
A new web site has been launched for the group. Please note that it is still under construction.