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Collisions and close encounters involving massive main-sequence stars

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Author

Summary, in English

We study close encounters involving massive main-sequence stars and the evolution of the exotic products of these encounters as common-envelope systems or possible hypernova progenitors. We show that parabolic encounters between low- and high-mass stars and between two high-mass stars with small periastrons result in mergers on time-scales of a few tens of stellar free-fall times (a few tens of hours). We show that such mergers of unevolved low-mass stars with evolved high-mass stars result in little mass-loss (similar to 0.01 M-circle dot) and can deliver sufficient fresh hydrogen to the core of the collision product to allow the collision product to burn for several million years. We find that grazing encounters enter a common-envelope phase which may expel the envelope of the merger product. The deposition of energy in the envelopes of our merger products causes them to swell by factors of similar to 100. If these remnants exist in very densely populated environments (n greater than or similar to 10(7) pc(-3)), they will suffer further collisions which may drive off their envelopes, leaving behind hard binaries. We show that the products of collisions have cores rotating sufficiently rapidly to make them candidate hypernova/gamma-ray burst progenitors and that similar to 0.1 per cent of massive stars may suffer collisions, sufficient for such events to contribute significantly to the observed rates of hypernovae and gamma-ray bursts.

Publishing year

2006

Language

English

Pages

1424-1436

Publication/Series

Monthly Notices of the Royal Astronomical Society

Volume

366

Issue

4

Document type

Journal article

Publisher

Oxford University Press

Topic

  • Astronomy, Astrophysics and Cosmology

Keywords

  • gamma-rays : bursts
  • blue stragglers
  • supernovae : general

Status

Published

ISBN/ISSN/Other

  • ISSN: 1365-2966