Stellar-mass black holes in the Hyades star cluster?

Abstract

Astrophysical models of binary-black hole mergers in the Universe require a significant fraction of stellar-mass black holes (BHs) to receive negligible natal kicks to explain the gravitational wave detections. This implies that BHs should be retained even in open clusters with low escape velocities ($\lesssim 1\mathrm{km}{\mathrm{s}}^{-1}$). We search for signatures of the presence of BHs in the nearest open cluster to the Sun - the Hyades - by comparing density profiles of direct $N$-body models to data from $Gaia$. The observations are best reproduced by models with $2-3$ BHs at present. Models that never possessed BHs have an half-mass radius $\sim 30\%$ smaller than the observed value, while those where the last BHs were ejected recently ($\lesssim 150$Myr ago) can still reproduce the density profile. In 50% of the models hosting BHs, we find BHs with stellar companion(s). Their period distribution peaks at $\sim 10^3$ yr, making them unlikely to be found through velocity variations. We look for potential BH companions through large $Gaia$ astrometric and spectroscopic errors, identifying 56 binary candidates - none of which consistent with a massive compact companion. Models with $2-3$ BHs have an elevated central velocity dispersion, but observations can not yet discriminate. We conclude that the present-day structure of the Hyades requires a significant fraction of BHs to receive natal kicks smaller than the escape velocity of $\sim 3\mathrm{km}{\mathrm{s}}^{-1}$ at the time of BH formation and that the nearest BHs to the Sun are in, or near, Hyades.

20 pages, 15 figures, 5 tables. Accepted for publication in MNRAS. Comments welcome

References in corpus (41)

• The Gaia mission
• Binary interaction dominates the evolution of massive stars
• galpy: A Python Library for Galactic Dynamics
• The Effect of Pair-Instability Mass Loss on Black Hole Mergers
• Improving the open cluster census. II. An all-sky cluster catalogue with Gaia DR3
• 4MOST: Project overview and information for the First Call for Proposals
• Clusters and mirages: cataloguing stellar aggregates in the Milky Way
• Merging black holes in young star clusters
• A catalog of newly identified star clusters in GAIA DR2
• Hunting for open clusters in \textit{Gaia} DR2: $582$ new OCs in the Galactic disc
• Black holes and core expansion in massive star clusters
• K2 rotation periods for low-mass Hyads and a quantitative comparison of the distribution of slow rotators in the Hyades and Praesepe
• PeTar: a high-performance N-body code for modeling massive collisional stellar systems
• On the structure of tidal tails
• Improving the open cluster census. I. Comparison of clustering algorithms applied to Gaia DR2 data
• Hunting for open clusters in Gaia EDR3: $628$ new open clusters found with OCfinder
• Extended stellar systems in the solar neighborhood - I. The tidal tails of the Hyades
• Ratios of star cluster core and half-mass radii: a cautionary note on intermediate-mass black holes in star clusters
• Astrometric Identification of Nearby Binary Stars I: Predicted Astrometric Signals
• The effect of stellar-mass black holes on the structural evolution of massive star clusters
• A stellar-mass black hole population in the globular cluster NGC 6101?
• Investigating mass segregation process in globular clusters with Blue Straggler Stars: the impact of dark remnants
• Praesepe (NGC 2632) and its tidal tails
• On the Mass of Dense Star Clusters in Starburst Galaxies from Spectro-Photometry
• A supra-massive population of stellar-mass black holes in the globular cluster Palomar 5
• A slow-down time-transformed symplectic integrator for solving the few-body problem
• A 3D view of the Hyades stellar and sub-stellar population
• Diagnosing the Stellar Population and Tidal Structure of the Blanco1 Star Cluster
• Kinematic modelling of clusters with Gaia: the Death Throes of the Hyades
• Dynamics of binary black holes in young star clusters: the impact of cluster mass and long-term evolution
• Spherical models of star clusters with potential escapers
• The impact of primordial binary on the dynamical evolution of intermediate massive star clusters
• Binary parameters from astrometric and spectroscopic errors--candidate hierarchical triples and massive dark companions in Gaia DR3
• The impact of massive stars and black holes on the fate of open star clusters and their tidal streams
• Astrophysical properties of 600 bonafide single stars in the Hyades open cluster
• Updated radial velocities and new constraints on the nature of the unseen source in NGC1850 BH1
• Effect of binarity in star cluster dynamical mass determination
• Mass Segregation in the Hyades Cluster
• Unraveling UBC 274: a morphological, kinematical and chemical analysis of a disrupting open cluster
• A simple two-component description of energy equipartition and mass segregation for anisotropic globular clusters
• A binary star sequence in the outskirts of the disrupting Galactic open cluster UBC 274

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