The R136 star cluster dissected with Hubble Space Telescope/STIS – II. Physical properties of the most massive stars in R136

Bestenlehner, J. M.; Crowther, P. A.; Caballero-Nieves, S. M.; Schneider, F. R. N.; Simón‐Díaz, S.; Brands, Sarah A.; Koter, A. de; Gräfener, G.; Herrero, A.; Langer, N.; Lennon, D. J.; Apellániz, J. Maíz; Puls, J.; Vink, J. S.

doi:10.1093/mnras/staa2801

Cited by 86 publications

(183 citation statements)

References 114 publications

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“…They showed that if the measured IMF of the R136 young massive cluster is granted to be canonical, as observations indicate, then the true highmass IMF of R136 at its birth must be at least moderately top-heavy when corrected for the dynamical escape of massive stars. A top-heavy IMF in R136 is further supported by a direct star-counts analysis (Bestenlehner et al 2020).…”

Section: Observational Evidence For a Systematically Varying Imfmentioning

confidence: 66%

The Lifetimes of Star Clusters Born with a Top-heavy IMF

Haghi

Safaei

Zonoozi

et al. 2020

ApJ

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Several observational and theoretical indications suggest that the initial mass function (IMF) becomes increasingly top-heavy (i.e., overabundant in high-mass stars with mass m > 1M) with decreasing metallicity and increasing gas density of the forming object. This affects the evolution of globular clusters (GCs) owing to the different mass-loss rates and the number of black holes formed. Previous numerical modeling of GCs usually assumed an invariant canonical IMF. Using the state-of-the-art NBODY6 code, we perform a comprehensive series of direct N-body simulations to study the evolution of star clusters, starting with a top-heavy IMF and undergoing early gas expulsion. Utilizing the embedded cluster mass-radius relation of Marks & Kroupa (2012) for initializing the models, and by varying the degree of top-heaviness, we calculate the minimum cluster mass needed for the cluster to survive longer than 12 Gyr. We document how the evolution of different characteristics of star clusters such as the total mass, the final size, the density, the mass-to-light ratio, the population of stellar remnants, and the survival of GCs is influenced by the degree of top-heaviness. We find that the lifetimes of clusters with different IMFs moving on the same orbit are proportional to the relaxation time to a power of x that is in the range of 0.8 to 1. The observed correlation between concentration and the mass function slope in Galactic GCs can be accounted for excellently in models starting with a top-heavy IMF and undergoing an early phase of rapid gas expulsion.

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Section: Observational Evidence For a Systematically Varying Imfmentioning

confidence: 66%

The Lifetimes of Star Clusters Born with a Top-heavy IMF

Haghi

Safaei

Zonoozi

et al. 2020

ApJ

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“…The upper mass limit is motivated by the observation of very massive stars ( ∼ 100 − 300 M ) in young, massive star formation regions such as those identified in the Tarantula Nebula (e.g. Bestenlehner et al 2020). Adopting a different upper mass limit has a negligible effect on the low mass stellar population considered in this work.…”

Section: Bpassmentioning

confidence: 99%

Binary evolution pathways of blue large-amplitude pulsators

Byrne

Stanway

Eldridge

2021

Monthly Notices of the Royal Astronomical Society

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Blue Large-Amplitude Pulsators (BLAPs) are a recently discovered class of pulsating star, believed to be proto-white dwarfs, produced by mass stripping of a red giant when it has a small helium core. An outstanding question is why the stars in this class of pulsator seem to form two distinct groups by surface gravity, despite predictions that stars in the gap between them should also pulsate. We use a binary population synthesis model to identify potential evolutionary pathways that a star can take to become a BLAP. We find that BLAPs can be produced either through common envelope evolution or Roche lobe overflow, with a Main Sequence star or an evolved compact object being responsible for the envelope stripping. The mass distribution of the inferred population indicates that fewer stars would be expected in the range of masses intermediate to the two known groups of pulsators, suggesting that the lack of observational discoveries in this region may be a result of the underlying population of pre-white dwarf stars. We also consider metallicity variation and find evidence that BLAPs at Z = 0.010 (half-Solar) would be pulsationally unstable and may also be more common. Based on this analysis, we expect the Milky Way to host around 12000 BLAPs and we predict the number density of sources expected in future observations such as the Legacy Survey of Space and Time at the Vera Rubin Observatory.

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“…The R136 star cluster in the 30 Dor region of the Large Magellanic Cloud (LMC) is a unique astrophysical laboratory; it is sufficiently young (1.5-2 Myr, de Koter et al 1998;Crowther et al 2016;Bestenlehner et al 2020) and rich (Crowther et al 2010) to allow the study of the formation and evolution of the most massive stars. Most of the information on R136 comes from Hubble Space Telescope (HST) observations, which was used to study various parameters including the cluster's star formation history, stellar content, and kinematics (Hunter et al 1995;Andersen et al 2009;De Marchi et al 2011;Cignoni et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Extreme adaptive optics astrometry of R136

Khorrami

Langlois

Vakili

et al. 2021

A&A

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We compared high-contrast near-infrared images of the core of R136 taken by VLT/SPHERE, in two epochs separated by 3.06 years. For the first time we monitored the dynamics of the detected sources in the core of R136 from a ground-based telescope with adaptive optics. The aim of these observations was to search for High prOper Motion cAndidates (HOMAs) in the central region of R136 (r < 6″) where it has been challenging for other instruments. Two bright sources (K < 15 mag and V < 16 mag) are located near R136a1 and R136c (massive WR stars) and have been identified as potential HOMAs. These sources have significantly shifted in the images with respect to the mean shift of all reliable detected sources and their neighbours, and six times their own astrometric errors. We calculate their proper motions to be 1.36 ± 0.22 mas yr−2 (321 ± 52 km s−1) and 1.15 ± 0.11 mas yr−2 (273 ± 26 km s−1). We discuss different possible scenarios to explain the magnitude of such extreme proper motions, and argue for the necessity to conduct future observations to conclude on the nature of HOMAs in the core of R136.

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The R136 star cluster dissected with Hubble Space Telescope/STIS – II. Physical properties of the most massive stars in R136

Cited by 86 publications

References 114 publications

The Lifetimes of Star Clusters Born with a Top-heavy IMF

The Lifetimes of Star Clusters Born with a Top-heavy IMF

Binary evolution pathways of blue large-amplitude pulsators

Extreme adaptive optics astrometry of R136

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