Gravitational conundrum? Dynamical mass segregation versus disruption of binary stars in dense stellar systems

Richard De Grijs*, Chengyuan Li, Yong Zheng, Licai Deng, Yi Hu, M. B.N. Kouwenhoven, James E. Wicker

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)


Upon their formation, dynamically cool (collapsing) star clusters will, within only a few million years, achieve stellar mass segregation for stars down to a few solar masses, simply because of gravitational two-body encounters. Since binary systems are, on average, more massive than single stars, one would expect them to also rapidly mass segregate dynamically. Contrary to these expectations and based on high-resolution Hubble Space Telescope observations, we show that the compact, 15-30 Myr old Large Magellanic Cloud cluster NGC 1818 exhibits tantalizing hints at the ≳ 2σ level of significance (>3σ if we assume a power-law secondary-to-primary mass-ratio distribution) of an increasing fraction of F-star binary systems (with combined masses of 1.3-1.6 M⊙) with increasing distance from the cluster center, specifically between the inner 10″-20″ (approximately equivalent to the cluster's core and half-mass radii) and the outer 60″-80″. If confirmed, then this will offer support for the theoretically predicted but thus far unobserved dynamical disruption processes of the significant population of "soft" binary systems - with relatively low binding energies compared to the kinetic energy of their stellar members - in star clusters, which we have access to here by virtue of the cluster's unique combination of youth and high stellar density.

Original languageEnglish
Article number4
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 1 Mar 2013
Externally publishedYes


  • HertzsprungRussell and C-M diagrams
  • Magellanic Clouds
  • binaries: general
  • galaxies: star clusters: individual (NGC 1818)
  • stars: kinematics and dynamics


Dive into the research topics of 'Gravitational conundrum? Dynamical mass segregation versus disruption of binary stars in dense stellar systems'. Together they form a unique fingerprint.

Cite this