Gravothermal oscillations in multicomponent models of star clusters

Breen, Philip G.; Heggie, Douglas C.

doi:10.1111/j.1365-2966.2012.21688.x

Cited by 20 publications

(15 citation statements)

References 18 publications

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“…This result is consistent with the criterion of Breen & Heggie (2012b) for gravothermal oscillations in multi-mass systems. They argued that gravothermal oscillations should occur for SCs in which N eff = M/mmax > ∼ 10 4 .…”

Section: Core Oscillations: Gravothermal or Not?supporting

confidence: 91%

The impact of metallicity-dependent mass-loss versus dynamical heating on the early evolution of star clusters

Trani

Mapelli

Bressan

2014

Monthly Notices of the Royal Astronomical Society

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We have run direct N-body simulations to investigate the impact of stellar evolution and dynamics on the structural properties of young massive (∼ 3 × 10 4 M ⊙ ) star clusters (SCs) with different metallicities (Z = 1, 0.1, 0.01 Z ⊙ ). Metallicity drives the mass loss by stellar winds and supernovae (SNe), with SCs losing more mass at high metallicity. We have simulated three sets of initial conditions, with different initial relaxation timescale. We find that the evolution of the half-mass radius of SCs depends on how fast two-body relaxation is with respect to the lifetime of massive stars. If core collapse is slow in comparison with stellar evolution, then mass loss by stellar winds and SNe is the dominant mechanism driving SC evolution, and metal-rich SCs expand more than metal-poor ones. In contrast, if core collapse occurs on a comparable timescale with respect to the lifetime of massive stars, then SC evolution depends on the interplay between mass loss and three-body encounters: dynamical heating by three-body encounters (mass loss by stellar winds and SNe) is the dominant process driving the expansion of the core in metal-poor (metal-rich) SCs. As a consequence, the half-mass radius of metal-poor SCs expands more than that of metal-rich ones. We also find core radius oscillations, which grow in number and amplitude as metallicity decreases.

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Section: Core Oscillations: Gravothermal or Not?supporting

confidence: 91%

The impact of metallicity-dependent mass-loss versus dynamical heating on the early evolution of star clusters

Trani

Mapelli

Bressan

2014

Monthly Notices of the Royal Astronomical Society

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“…The conditions for the onset of gravothermal oscillations in two-component models have been studied by Breen & Heggie (2012a), who found that the value of N2 (the number of heavy stars) could be used as an approximate stability condition (where the stability boundary is at N2 ∼ 3000) for a wide range of stellar and total mass ratios (2 m2/m1 50 and 0.1 M2/M1 1.0). Breen & Heggie (2012b), who researched the onset of gravothermal oscillation in multicomponent systems, found that the parameter called the effective particle number N ef (defined as M/mmax) could be used as an approximate stability condition for both the multi-component systems they studied and the twocomponent models of Breen & Heggie (2012a). The stability boundary they found was at N ef ∼ 10 4 , which is also consistent with the stability boundary of the one-component model at N = 7000 (Goodman 1987).…”

Section: Gravothermal Oscillationssupporting

confidence: 59%

Dynamical evolution of black hole subsystems in idealized star clusters

Breen¹,

Heggie²

2013

Monthly Notices of the Royal Astronomical Society

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In this paper, globular star clusters which contain a sub-system of stellar-mass black holes (BH) are investigated. This is done by considering two-component models, as these are the simplest approximation of more realistic multi-mass systems, where one component represents the BH population and the other represents all the other stars. These systems are found to undergo a long phase of evolution where the centre of the system is dominated by a dense BH sub-system. After mass segregation has driven most of the BH into a compact sub-system, the evolution of the BH sub-system is found to be influenced by the cluster in which it is contained. The BH sub-system evolves in such a way as to satisfy the energy demands of the whole cluster, just as the core of a one component system must satisfy the energy demands of the whole cluster. The BH sub-system is found to exist for a significant amount of time. It takes approximately 10t rh,i , where t rh,i is the initial half-mass relaxation time, from the formation of the compact BH sub-system up until the time when 90% of the sub-system total mass is lost (which is of order 10 3 times the half-mass relaxation time of the BH subsystem at its time of formation). Based on theoretical arguments the rate of mass loss from the BH sub-system (Ṁ 2 ) is predicted to be −βζM/(αt rh ), where M is the total mass, t rh is the half-mass relaxation time, and α, β, ζ are three dimensionless parameters (see Section 2 for details). An interesting consequence of this is that the rate of mass loss from the BH sub-system is approximately independent of the stellar mass ratio (m 2 /m 1 ) and the total mass ratio (M 2 /M 1 ) (in the range m 2 /m 1 10 and M 2 /M 1 ∼ 10 −2 , where m 1 , m 2 are the masses of individual low-mass and high-mass particles respectively, and M 1 , M 2 are the corresponding total masses). The theory is found to be in reasonable agreement with most of the results of a series of N-body simulations, and with all of the models if the value of ζ is suitable adjusted. Predictions based on theoretical arguments are also made about the structure of BH sub-systems. Other aspects of the evolution are also considered such as the conditions for the onset of gravothermal oscillation. out any supernova explosion (Fryer 1999). Uncertainty in the natal kicks leads to uncertainty in the initial size of the BH population. As the BH are more massive than the other stars in the system, any retained BH will undergo mass segregation and almost all are likely to become concentrated in the centre of the system, eventually forming a compact sub-system.The mass of the BH sub-system decreases over time because BH binaries form in the dense core of the BH subsystem, causing the ejection of single BH and ultimately the binaries themselves through super-elastic encounters (see

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“…Beccari et al suggest that these generations of blue stragglers formed during brief periods of increased stellar density caused by core collapse and by the oscillations that occur after core collapse (e.g. Bettwieser & Sugimoto 1984;Goodman 1987;Cohn, Hut & Wise 1989;Takahashi & Inagaki 1991;Breen & Heggie 2012). The complicated velocity field of the centre M15 may also be due to these post core collapse oscillations.…”

Section: Discussionmentioning

confidence: 99%

MUSE narrow field mode observations of the central kinematics of M15

Usher

Kamann

Gieles

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We present observations of the stellar kinematics of the centre of the core collapsed globular cluster M15 obtained with the MUSE integral field spectrograph on the VLT operating in narrow field mode. Thanks to the use of adaptive optics, we obtain a spatial resolution of 0.1 arcsec and are able to reliably measure the radial velocities of 864 stars within 8 arcsec of the centre of M15 thus providing the largest sample of radial velocities ever obtained for the innermost regions of this system. Combined with previous observations of M15 using MUSE in wide field mode and literature data, we find that the central kinematics of M15 are complex with the rotation axis of the core of M15 offset from the rotation axis of the bulk of the cluster. While this complexity has been suggested by previous work, we confirm it at higher significance and in more detail.

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Gravothermal oscillations in multicomponent models of star clusters

Cited by 20 publications

References 18 publications

The impact of metallicity-dependent mass-loss versus dynamical heating on the early evolution of star clusters

The impact of metallicity-dependent mass-loss versus dynamical heating on the early evolution of star clusters

Dynamical evolution of black hole subsystems in idealized star clusters

MUSE narrow field mode observations of the central kinematics of M15

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