Forming short period sub-stellar companions in 47 Tuc: I. Dynamical model and brown dwarf tidal capture rates

Abstract

Stars in globular clusters formed and evolved in the most extreme environment: high density and low metallicity. If the formation of stars and planets are at all sensitive to environmental conditions, this should therefore be evident in globular clusters. Observations have indicated that hot Jupiters are at least an order of magnitude less prevalent in the central region of the globular cluster 47 Tucanae than in the field. In this work, we explore the claims in the literature for additional consequences for the low mass stellar initial mass function. Tidal capture, the mechanism that produces X-ray binaries in globular clusters, applies also to brown dwarfs (BDs). This process produces tight stellar-BD binaries that would be detectable by transit surveys. Applying a Monte Carlo dynamical evolution model, we compute the overall BD capture rates. We find that the number of captures is lower than previous estimates. Capture efficiency increases steeply with stellar mass, which means that mass segregation reduces capture efficiency as BDs and low mass stars occupy the same regions. The result of this effect is that the current constraints on the short period companion fraction remains marginally consistent with initially equal numbers of BDs and stars. However, our findings suggest that expanding the sample in 47 Tuc or surveying other globular clusters for close sub-stellar companions can yield constraints on the sub-stellar initial mass function in these environments. We estimate the capture rates in other globular clusters and suggest that 47 Tuc remains a promising target for future transit surveys.

arXiv comment15 pages, 13 figures, accepted for publication in MNRAS

References in corpus (41)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Galactic Stellar and Substellar Initial Mass Function
• Evolution of binary stars and the effect of tides on binary populations
• Comprehensive analytic formulae for stellar evolution as a function of mass and metallicity
• galpy: A Python Library for Galactic Dynamics
• First Results from High Angular Resolution ALMA Observations Toward the HL Tau Region
• The Formation of Brown Dwarfs as Ejected Stellar Embryos
• Stellar, brown dwarf and multiple star properties from a radiation hydrodynamical simulation of star cluster formation
• Two accreting protoplanets around the young star PDS 70
• The Luminosity & Mass Function of the Trapezium Cluster: From B stars to the Deuterium Burning Limit
• The Frequency of Hot Jupiters Orbiting Nearby Solar-Type Stars
• Stellar Collisions During Binary-Binary and Binary-Single Star Interactions
• The Big Problems in Star Formation: the Star Formation Rate, Stellar Clustering, and the Initial Mass Function
• The Formation of Close Binary Systems by Dynamical Interactions and Orbital Decay
• Orbital and atmospheric characterization of the planet within the gap of the PDS 70 transition disk
• Dynamical evolution of black hole sub-systems in idealised star clusters
• Effects of Tidal Shocks on the Evolution of Globular Clusters
• The Formation of Free-Floating Brown Dwarves and Planetary-Mass Objects by Photo-Erosion of Prestellar Cores
• Gravitational fragmentation and the formation of brown dwarfs in stellar clusters
• Evidence of an Upper Bound on the Masses of Planets and its Implications for Giant Planet Formation
• Fragmentation of Molecular Clouds: The Initial Phase of a Stellar Cluster
• MOCCA Code for Star Cluster Simulations - II. Comparison with N-body Simulations
• The Initial Mass Function of the Orion Nebula Cluster across the H-burning limit
• MOCCA code for star cluster simulations - I. Blue Stragglers, first results
• A new Monte Carlo code for star cluster simulations: II. Central black hole and stellar collisions
• A Census of Young Stars and Brown Dwarfs in IC 348 and NGC 1333
• Hot Jupiters are Destroyed by Tides While Their Host Stars are on the Main Sequence
• Evidence for a Turnover in the IMF of Low Mass Stars and Sub-stellar Objects: Analysis from an Ensemble of Young Clusters
• Evidence for a circumplanetary disk around protoplanet PDS 70 b
• Monte Carlo Simulations of Star Clusters - VII. The globular cluster 47 Tuc
• Monte Carlo simulations of star clusters - II. Tidally limited, multi-mass systems with stellar evolution
• Search for giant planets in M67 III: excess of hot Jupiters in dense open clusters
• Giant planet and brown dwarf formation
• MOCCA Survey Database I: Dissolution of tidally filling star clusters harbouring BH subsystems
• Monte-Carlo Simulations of Star Clusters I. First Results
• The bimodal initial mass function in the Orion Nebula Cloud
• Substellar Objects in Nearby Young Clusters VII: The substellar mass function revisited
• Galactic globular clusters: a new catalog of masses, structural parameters, velocity dispersion profiles, proper motions and space orbits
• Are there brown dwarfs in globular clusters?
• An upper limit for the growth of inner planets?
• Chaos and Tidal Capture

Cited by in corpus (3)

• Accretion of sub-stellar companions as the origin of chemical abundance inhomogeneities in globular clusters
• Forming short period sub-stellar companions in 47 Tucanae -- II. Analytic expressions for the orbital evolution of planets in dense environments
• Uncovering the Rapidly Evolving Orbits of the Dynamic TOI-201 System