Substellar companions and isolated planetary-mass objects from protostellar disc fragmentation

WKM Rice, PJ Armitage, Ian Alexander Bonnell, MR Bate, SV Jeffers, SG Vine

Research output: Contribution to journalArticlepeer-review

82 Citations (Scopus)

Abstract

Self-gravitating protostellar discs are unstable to fragmentation if the gas can cool on a time-scale that is short compared with the orbital period. We use a combination of hydrodynamic simulations and N-body orbit integrations to study the long-term evolution of a fragmenting disc with an initial mass ratio to the star of M-disc/M-* = 0.1. For a disc that is initially unstable across a range of radii, a combination of collapse and subsequent accretion yields substellar objects with a spectrum of masses extending (for a Solar-mass star) up to approximate to0.01 M-.. Subsequent gravitational evolution ejects most of the lower mass objects within a few million years, leaving a small number of very massive planets or brown dwarfs in eccentric orbits at moderately small radii. Based on these results, systems such as HD 168443 - in which the companions are close to or beyond the deuterium burning limit - appear to be the best candidates to have formed via gravitational instability. If massive substellar companions originate from disc fragmentation, while lower-mass planetary companions originate from core accretion, the metallicity distribution of stars which host massive substellar companions at radii of similar to1 au should differ from that of stars with lower mass planetary companions.

Original languageEnglish
Pages (from-to)L36-L40
Number of pages5
JournalMonthly Notices of the Royal Astronomical Society
Volume346
Issue number3
Publication statusPublished - 11 Dec 2003

Keywords

  • accretion, accretion discs
  • planets and satellites : formation
  • stars : low-mass, brown dwarfs
  • planetary systems : protoplanetary discs
  • stars : pre-main sequence
  • 3-DIMENSIONAL HYDRODYNAMIC INSTABILITIES
  • FREE-FLOATING PLANETS
  • GRAVITATIONAL INSTABILITIES
  • GIANT PLANETS
  • PROTOPLANETARY DISKS
  • CIRCUMSTELLAR DISKS
  • EXTRASOLAR PLANETS
  • THERMAL ENERGETICS
  • STELLAR CLUSTERS
  • BINARY-SYSTEMS

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