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Close stellar encounters at the Galactic Centre - I. The effect on the observed stellar populations

Mastrobuono-Battisti, Alessandra LU ; Church, Ross P. LU orcid and Davies, Melvyn B. LU (2021) In Monthly Notices of the Royal Astronomical Society 505(3). p.3314-3328
Abstract
We model the effects of collisions and close encounters on the stellar populations observed in the Milky Way nuclear
stellar cluster (NSC). Our analysis is based on N -body simulations in which the NSC forms by accretion of massive
stellar clusters around a supermassive black hole. We attach stellar populations to our N -body particles and follow the
evolution of their stars, and the rate of collisions and close encounters. The most common encounters are collisions
between pairs of main-sequence stars, which lead to mergers: destructive collisions between main-sequence stars
and compact objects are rare. We find that the effects of collisions on the stellar populations are small for three
reasons. First, our models... (More)
We model the effects of collisions and close encounters on the stellar populations observed in the Milky Way nuclear
stellar cluster (NSC). Our analysis is based on N -body simulations in which the NSC forms by accretion of massive
stellar clusters around a supermassive black hole. We attach stellar populations to our N -body particles and follow the
evolution of their stars, and the rate of collisions and close encounters. The most common encounters are collisions
between pairs of main-sequence stars, which lead to mergers: destructive collisions between main-sequence stars
and compact objects are rare. We find that the effects of collisions on the stellar populations are small for three
reasons. First, our models possess a core which limits the maximum stellar density. Secondly, the velocity dispersion
in the NSC is similar to the surface escape velocities of the stars, which minimises the collision rate. Finally, whilst
collisions between main-sequence stars destroy bright giants by accelerating their evolution, they also create them
by accelerating the evolution of lower-mass stars. These two effects approximately cancel out. We also investigate
whether the G2 cloud could be a fuzzball: a compact stellar core which has accreted a tenuous envelope in a close
encounter with a red giant. We conclude that fuzzballs with cores below 2 M have thermal times-scales too short
to reproduce G2. A fuzzball with a black-hole core could reproduce the surface properties of G2 but the production
rate of such objects in our model is low. (Less)
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author
; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
methods: numerical, stars: evolution, Galaxy: evolution, Galaxy: nucleus, Galaxy: stellar content, Astrophysics - Astrophysics of Galaxies
in
Monthly Notices of the Royal Astronomical Society
volume
505
issue
3
pages
15 pages
publisher
Oxford University Press
external identifiers
  • scopus:85122521931
ISSN
1365-2966
DOI
10.1093/mnras/stab1409
language
English
LU publication?
yes
id
ff59872f-dc46-4bbc-b7ba-24021e5aef99
date added to LUP
2022-03-28 13:10:50
date last changed
2024-04-16 23:49:44
@article{ff59872f-dc46-4bbc-b7ba-24021e5aef99,
  abstract     = {{We model the effects of collisions and close encounters on the stellar populations observed in the Milky Way nuclear<br/>stellar cluster (NSC). Our analysis is based on N -body simulations in which the NSC forms by accretion of massive<br/>stellar clusters around a supermassive black hole. We attach stellar populations to our N -body particles and follow the<br/>evolution of their stars, and the rate of collisions and close encounters. The most common encounters are collisions<br/>between pairs of main-sequence stars, which lead to mergers: destructive collisions between main-sequence stars<br/>and compact objects are rare. We find that the effects of collisions on the stellar populations are small for three<br/>reasons. First, our models possess a core which limits the maximum stellar density. Secondly, the velocity dispersion<br/>in the NSC is similar to the surface escape velocities of the stars, which minimises the collision rate. Finally, whilst<br/>collisions between main-sequence stars destroy bright giants by accelerating their evolution, they also create them<br/>by accelerating the evolution of lower-mass stars. These two effects approximately cancel out. We also investigate<br/>whether the G2 cloud could be a fuzzball: a compact stellar core which has accreted a tenuous envelope in a close<br/>encounter with a red giant. We conclude that fuzzballs with cores below 2 M  have thermal times-scales too short<br/>to reproduce G2. A fuzzball with a black-hole core could reproduce the surface properties of G2 but the production<br/>rate of such objects in our model is low.}},
  author       = {{Mastrobuono-Battisti, Alessandra and Church, Ross P. and Davies, Melvyn B.}},
  issn         = {{1365-2966}},
  keywords     = {{methods: numerical; stars: evolution; Galaxy: evolution; Galaxy: nucleus; Galaxy: stellar content; Astrophysics - Astrophysics of Galaxies}},
  language     = {{eng}},
  month        = {{08}},
  number       = {{3}},
  pages        = {{3314--3328}},
  publisher    = {{Oxford University Press}},
  series       = {{Monthly Notices of the Royal Astronomical Society}},
  title        = {{Close stellar encounters at the Galactic Centre - I. The effect on the observed stellar populations}},
  url          = {{http://dx.doi.org/10.1093/mnras/stab1409}},
  doi          = {{10.1093/mnras/stab1409}},
  volume       = {{505}},
  year         = {{2021}},
}