Blue supergiants as tests for stellar physics

Abstract

Massive star evolution is still poorly understood, and observational tests are required to discriminate between different implementations of physical phenomenon in stellar evolution codes. By confronting stellar evolution models with observed properties of blue supergiants, such as pulsations, chemical composition and position in the Hertzsprung-Russell diagram, we aim at determining which of the criterion used for convection (Schwarzschild or Ledoux) is best able to explain the observations. We compute state-of-the-art stellar evolution models with either the Schwarzschild or the Ledoux criterion for convection. Models are for $14$ to $35M_{\odot }$ at solar or Large Magellanic Cloud metallicity. For each model, we compute the pulsation properties to know when radial modes are excited. We then compare our results with the position of blue supergiants in the Hertzsprung-Russell diagram, with their surface chemical composition, and with their variability. Our results at Large Magellanic Cloud metallicity shows only a slight preference for the Ledoux criterion over the Schwarzschild one in reproducing at the same time the observed properties of blue supergiants, even if the Schwarzschild criterion cannot be excluded at this metallicity. We check that changing the overshoot parameter at solar metallicity does not improve the situation. We also check that our models are able to reproduce the position of Galactic blue supergiant in the flux-weighted-gravity -- luminosity relation. We confirm that overall, models computed with the Ledoux criterion are slightly better in matching observations. Our results also support the idea that most Galactic $\alpha$ Cyg variables are blue supergiants of the group 2, i.e. stars that have been through a previous red supergiant phase where they have lost large amount of mass.

14 pages, 10 figures, accepted for publication in A&A

References in corpus (17)

• The Gaia mission
• The VLT-FLAMES survey of massive stars: constraints on stellar evolution from the chemical compositions of rapidly rotating Galactic and Magellanic Cloud B-type stars
• The spectroscopic Hertzsprung-Russell diagram of Galactic massive stars
• The impact of mass-loss on the evolution and pre-supernova properties of red supergiants
• Quantitative studies of the optical and UV spectra of Galactic early B supergiants I. Fundamental parameters
• Constraining mixing in massive stars in the Small Magellanic Cloud
• The MiMeS Survey of Magnetism in Massive Stars: CNO surface abundances of Galactic O stars
• Evolution of surface CNO abundances in massive stars
• Convective core entrainment in 1D main sequence stellar models
• LMC Blue Supergiant Stars and the Calibration of the Flux-weighted Gravity--Luminosity Relationship
• Automated classification of Hipparcos unsolved variables
• Quantitative spectroscopy of Galactic BA-type supergiants. I. Atmospheric parameters
• SNAPSHOT: Connections between Internal and Surface Properties of Massive Stars
• Spectroscopic and photometric oscillatory envelope variability during the S Doradus outburst of the Luminous Blue Variable R71
• Pulsations as a Driver for LBV Variability
• A massive nebula around the Luminous Blue Variable star RMC143 revealed by ALMA
• Mixing of CNO-cycled matter in massive stars

Cited by in corpus (14)

• Convective boundary mixing in main-sequence stars: theory and empirical constraints
• Numerical experiments to help understand cause and effect in massive star evolution
• Schwarzschild and Ledoux are equivalent on evolutionary timescales
• Clumping and X-Rays in cooler B supergiant stars
• The IACOB project X. Large-scale quantitative spectroscopic analysis of Galactic luminous blue stars
• The IACOB project IX. Building a modern empirical database of Galactic O9-B9 supergiants: sample selection, description, and completeness
• A Panchromatic Study of Massive Stars in the Extremely Metal-Poor Local Group Dwarf Galaxy Leo A
• The impact of convective criteria on the properties of massive stars
• Binarity at LOw Metallicity (BLOeM): The multiplicity properties and evolution of BAF-type supergiants
• Decoding the X-ray flare from MAXI J0709-159 using optical spectroscopy and multi-epoch photometry
• Convective Mixing: The Formation Channel of Li-rich Giants
• Unveiling the evolutionary state of three B supergiant stars: PU Gem, $\epsilon$ CMa and $\eta$ CMa
• Photometric and spectroscopic variability of the blue supergiant rho Leo
• The Properties of Fast Yellow Pulsating Supergiants: FYPS Point the Way to Missing Red Supergiants