The influence of black holes on the binary population of the globular cluster Palomar 5

Long Wang*, Mark Gieles, Holger Baumgardt, Chengyuan Li, Xiaoying Pang, Baitian Tang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

The discovery of stellar-mass black holes (BHs) in globular clusters (GCs) raises the possibility of long-term retention of BHs within GCs. These BHs influence various astrophysical processes, including merger-driven gravitational waves and the formation of X-ray binaries. They also impact cluster dynamics by heating and creating low-density cores. Previous N-body models suggested that Palomar 5, a low-density GC with long tidal tails, may contain more than 100 BHs. To test this scenario, we conduct N-body simulations of Palomar 5 with primordial binaries to explore the influence of BHs on binary populations and the stellar mass function. Our results show that primordial binaries have minimal effect on the long-term evolution. In dense clusters with BHs, the fraction of wide binaries with periods >105 d decreases, and the disruption rate is independent of the initial period distribution. Multi-epoch spectroscopic observations of line-of-sight velocity changes can detect most bright binaries with periods below 104 d, significantly improving velocity dispersion measurements. Four BH-MS binaries in the model with BHs suggests their possible detection through the same observation method. Including primordial binaries leads to a flatter inferred mass function because of spatially unresolved binaries, leading to a better match of the observations than models without binaries, particularly in Palomar 5's inner region. Future observations should focus on the cluster velocity dispersion and binaries with periods of 104-105 d in Palomar 5's inner and tail regions to constrain BH existence.

Original languageEnglish
Pages (from-to)7495-7514
Number of pages20
JournalMonthly Notices of the Royal Astronomical Society
Volume527
Issue number3
DOIs
Publication statusPublished - 1 Jan 2024

Keywords

  • binaries: general
  • globular clusters: individual: Palomar 5
  • methods: numerical
  • stars: black holes
  • techniques: radial velocities

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