Searching for compact objects in the single-lined spectroscopic binaries of the young Galactic cluster NGC 6231

Abstract

Recent evolutionary computations predict that a few percent of massive OB stars in binary systems should have a dormant BH companion. Despite several reported X-ray quiet OB+BH systems over the last couple of years, finding them with certainty remains challenging. These have great importance as they can be gravitational wave (GW) source progenitors, and are landmark systems in constraining supernova kick physics. This work aims to characterise the hidden companions to the single-lined spectroscopic binaries (SB1s) in the B star population of the young open Galactic cluster NGC 6231 to find candidate systems for harbouring compact object companions. With the orbital solutions for each SB1 previously constrained, we applied Fourier spectral disentangling to multi-epoch optical VLT/FLAMES spectra of each target to extract a potential signature of a faint companion, and to identify newly disentangled double-lined spectroscopic binaries (SB2s). For targets where the disentangling does not reveal any signature of a stellar companion, we performed atmospheric and evolutionary modelling on the primary to obtain constraints on the unseen companion. Seven newly classified SB2 systems with mass ratios down to near 0.1 were identified. From the remaining targets, for which no faint companion could be extracted from the spectra, four are found to have companion masses in the predicted mass ranges of neutron stars (NSes) and BHes. Two of these have companion masses between 1 and 3.5 $M_{\odot }$, making them potential hosts of NSes (or lower mass main sequence stars). The other two are between 2.5 to 8 $M_{\odot }$ and 1.6 and 26 $M_{\odot }$, respectively, and so are identified as candidates for harbouring BH companions. However, unambiguous identification of these systems as X-ray quiet compact object harbouring binaries requires follow up observations.

Submitted to A&A

References in corpus (40)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Binary interaction dominates the evolution of massive stars
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• A Grid of NLTE Line-Blanketed Model Atmospheres of Early B-type Stars
• Southern Massive Stars at High Angular Resolution: Observational Campaign and Companion Detection
• Second ROSAT all-sky survey (2RXS) source catalogue
• Cygnus X-1 contains a 21-solar mass black hole -- implications for massive star winds
• Rotational mixing in massive binaries: detached short-period systems
• A wide star-black-hole binary system from radial-velocity measurements
• BONNSAI: a Bayesian tool for comparing stars with stellar evolution models
• The role of mass transfer and common envelope evolution in the formation of merging binary black holes
• An XMM-Newton view of the young open cluster NGC 6231 -- II. The OB star population
• The Tarantula Massive Binary Monitoring: I. Observational campaign and OB-type spectroscopic binaries
• Pre-supernova evolution, compact object masses and explosion properties of stripped binary stars
• Is HR 6819 a triple system containing a black hole? -- An alternative explanation
• Hypercritical Accretion, Induced Gravitational Collapse, and Binary-Driven Hypernovae
• A naked-eye triple system with a nonaccreting black hole in the inner binary
• An X-ray quiet black hole born with a negligible kick in a massive binary within the Large Magellanic Cloud
• Detailed models of interacting short-period massive binary stars
• Identifying quiescent compact objects in massive Galactic single-lined spectroscopic binaries
• The VLT-FLAMES Tarantula Survey XVIII. Classifications and radial velocities of the B-type stars
• Chemically Homogeneous Evolution: A rapid population synthesis approach
• The Tarantula Massive Binary Monitoring VI: Characterisation of hidden companions in 51 single-lined O-type binaries, a flat mass-ratio distribution, and black-hole binary candidates
• The presupernova core mass-radius relation of massive stars: understanding its formation and evolution
• A black hole detected in the young massive LMC cluster NGC 1850
• The young massive SMC cluster NGC 330 seen by MUSE II. Multiplicity properties of the massive-star population
• Population Synthesis of Black Hole Binaries with Normal-Star Companions: I. Detached Systems
• The Tarantula Massive Binary Monitoring. IV. Double-lined photometric binaries
• An XMM-Newton view of the young open cluster NGC 6231 III. Optically faint X-ray sources
• Constraining the Overcontact Phase in Massive Binary Evolution I. Mixing in V382 Cyg, VFTS 352, and OGLE SMC-SC10 108086
• HR 6819 is a binary system with no black hole -- revisiting the source with infrared interferometry and optical integral field spectroscopy
• BONNSAI: correlated stellar observables in Bayesian methods
• Optical Analysis and Modeling of HD96670, a new Black Hole X-ray Binary Candidate
• A Chandra X-ray study of the young star cluster NGC 6231: low-mass population and initial mass function
• MONOS.II. Orbit review and analysis for 35 single-lined spectroscopic binary systems and candidates
• Confirming NGC 6231 as the parent cluster of the runaway high-mass X-ray binary HD 153919/4U 1700-37 with Gaia DR2
• A Survey for High-Mass Eclipsing Binaries
• The H-alpha Emission Line Variations of HR 6819
• Resolving the dynamical mass tension of the massive binary 9 Sagittarii

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