Formation of ultracompact x-ray binaries in dense star clusters

N. Ivanova*, F. A. Rasio, J. C. Lombardi, K. L. Dooley, Z. F. Proulx

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Bright, ultracompact X-ray binaries observed in dense star clusters, such as Galactic globular clusters, must have formed relatively recently, since their lifetimes as persistent bright sources are short (e.g., ∼10 8 yr above 1036 ergs s-1 for a 1.4 M⊙ neutron star accreting from a degenerate helium companion with an initial mass of ∼0.2 M⊙). Therefore, we can use the present conditions in a cluster core to study possible dynamical formation processes for these sources. Here we show that direct physical collisions between neutron stars and red giants can provide a sufficient formation rate to explain the observed numbers of bright sources. These collisions produce tight, eccentric neutron star-white dwarf binaries that decay to contact by gravitational radiation on timescales ∼106-1010 yr, usually shorter and often much shorter than the cluster age.

Original languageEnglish (US)
Pages (from-to)L109-L112
JournalAstrophysical Journal
Issue number2 II
StatePublished - Mar 10 2005


  • Binaries: Close
  • Galaxies: Star clusters
  • Globular clusters: General
  • Hydrodynamics -stellar dynamics
  • X-rays: Binaries

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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