On the evolutionary nature of puffed-up stripped star binaries and their occurrence in stellar populations

Abstract

The majority of massive stars are formed in multiple systems and will interact with companions via mass transfer. This interaction typically leads to the primary shedding its envelope and the formation of a "stripped star". Classically, stripped stars are expected to quickly contract to become hot UV-bright helium stars. Surprisingly, recent optical surveys have unveiled a large number of stripped stars that are larger and cooler, appearing "puffed-up" and overlapping with the Main Sequence (MS). Here, we study the evolutionary nature and lifetimes of puffed-up stripped (PS) stars using stellar-evolution code MESA. We computed grids of binary models at four metallicities from Z = 0.017 to 0.0017. Contrary to previous assumptions, we find that stripped stars regain thermal equilibrium shortly after the end of mass transfer. Their further contraction is determined by the rate at which the residual H-rich envelope is depleted, with the main agents being H-shell burning (dominant) and mass-loss in winds. The duration of the PS star phase is 1$\%$ of the total lifetime and up to 100 times more than thermal timescale. We explored several relevant factors: orbital period, mass ratio, winds, and semiconvection. We carried out a simple population estimation, finding that $\sim$0.5-0.7 $\%$ of all the stars with $\log (L/L_{\odot }$) $>$ 3.7 are PS stars. Our results indicate that tens to hundred of PS stars may be hiding in the MS population, disguised as normal stars: $\sim$100 in the Small Magellanic Cloud alone. Their true nature may be revealed by low surface gravities, high N enrichment, and likely slow rotations

12 pages, 10 figures, 2 tables, (+appendices), submitted to A&A

References in corpus (37)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Binary interaction dominates the evolution of massive stars
• Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
• Southern Massive Stars at High Angular Resolution: Observational Campaign and Companion Detection
• Modules for Experiments in Stellar Astrophysics (MESA): Time-Dependent Convection, Energy Conservation, Automatic Differentiation, and Infrastructure
• The effect of massive binaries on stellar populations and supernova progenitors
• New PARSEC evolutionary tracks of massive stars at low metallicity: testing canonical stellar evolution in nearby star forming dwarf galaxies
• Updated Electron-Conduction Opacities: The Impact on Low-Mass Stellar Models
• The evolution of runaway stellar collision products
• A wide star-black-hole binary system from radial-velocity measurements
• Formation of Double Compact Objects
• On the nature of massive helium star winds and Wolf-Rayet-type mass loss
• Different to the core: the pre-supernova structures of massive single and binary-stripped stars
• The VMC Survey - XIV. First results on the look-back time star-formation rate tomography of the Small Magellanic Cloud
• Constraining mixing in massive stars in the Small Magellanic Cloud
• Populations of rotating stars III. SYCLIST, the new Geneva Population Synthesis code
• Evolutionary Models for Type Ib/c Supernova Progenitors
• Why binary interaction does not necessarily dominate the formation of Wolf-Rayet stars at low metallicity
• Is HR 6819 a triple system containing a black hole? -- An alternative explanation
• Grids of stellar models with rotation IV. Models from 1.7 to 120 Msun at a metallicity Z = 0.0004
• A naked-eye triple system with a nonaccreting black hole in the inner binary
• The Detection and Characterization of Be+sdO Binaries from HST/STIS FUV Spectroscopy
• Massive donors in interacting binaries: effect of metallicity
• Partial-envelope stripping and nuclear-timescale mass transfer from evolved supergiants at low metallicity
• Detection of the Ultraviolet Spectrum of the Hot Subdwarf Companion of 60 Cygni (B1 Ve) from a Survey of IUE Spectra of Be Stars
• The qWR star HD 45166. II. Fundamental stellar parameters and evidence of a latitude-dependent wind
• The contribution from stars stripped in binaries to cosmic reionization of hydrogen and helium
• Binary-Stripped Stars as Core-Collapse Supernovae Progenitors
• A massive helium star with a sufficiently strong magnetic field to form a magnetar
• Population Synthesis of Galactic Be-star Binaries with A Helium-star Companion
• Numerical experiments to help understand cause and effect in massive star evolution
• A dearth of young and bright massive stars in the Small Magellanic Cloud
• A partially stripped massive star in a Be binary at low metallicity: A missing link towards Be X-ray binaries and double neutron star mergers
• The B-type Binaries Characterisation Programme II. VFTS 291: A stripped star from a recent mass transfer phase
• $\gamma$ Columbae: the recently stripped, pulsating core of a massive star
• Updated radial velocities and new constraints on the nature of the unseen source in NGC1850 BH1
• Binaries at Low Metallicity: ranges for case A, B and C mass transfer

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