The spectroscopic Hertzsprung-Russell diagram of hot massive stars in the SMC

Abstract

We present a comprehensive stellar atmosphere analysis of 329 O- and B-type stars in the Small Magellanic Cloud (SMC) from the RIOTS4 survey. Using spectroscopically derived effective temperature (Teff) and surface gravities, we find that classical Be stars appear misplaced to low Teff and high luminosity in the spectroscopic Hertzsprung-Russell diagram (sHRD). Together with the most luminous stars in our sample, the stellar masses derived from the sHRD for these objects are systematically larger than those obtained from the conventional HRD. This suggests that the well-known, spectroscopic mass-discrepancy problem may be linked to the fact that both groups of stars have outer envelopes that are nearly gravitationally unbound. The non-emission-line stars in our sample mainly appear on the main-sequence, allowing a first estimate of the terminal-age main-sequence (TAMS) in the SMC, which matches the predicted TAMS between 12 and 40M${}_{\odot }$ at SMC metallicity. We further find a large underabundance of stars above $\sim 25$M${}_{\odot }$ near the ZAMS, reminiscent of such earlier findings in the Milky Way and LMC.

22 pages, 12 figures, 1 table; accepted for publication in ApJ

References in corpus (21)

• Binary interaction dominates the evolution of massive stars
• The Supernova -- Gamma-Ray Burst Connection
• Pre-Supernova Evolution of Massive Single and Binary Stars
• Present-day cosmic abundances. A comprehensive study of nearby early B-type stars and implications for stellar and Galactic evolution and interstellar dust models
• The Supernova Channel of Super-AGB Stars
• The role of stellar feedback in the formation of galaxies
• An excess of massive stars in the local 30 Doradus starburst
• The VLT-FLAMES survey of massive stars: Evolution of surface N abundances and effective temperature scales in the Galaxy and Magellanic Clouds
• Spitzer SAGE-SMC Infrared Photometry of Massive Stars in the Small Magellanic Cloud
• The VLT-FLAMES survey of massive stars: Mass loss and rotation of early-type stars in the SMC
• The spectroscopic Hertzsprung-Russell diagram
• The spectroscopic Hertzsprung-Russell diagram of Galactic massive stars
• The IACOB project: III. New observational clues to understand macroturbulent broadening in massive O- and B-type stars
• The VMC Survey. XXV. The 3D structure of the Small Magellanic Cloud from Classical Cepheids
• The IACOB project. V. Spectroscopic parameters of the O-type stars in the modern grid of standards for spectral classification
• Spectroscopic and physical parameters of Galactic O-type stars. III. Mass discrepancy and rotational mixing
• The metallicity dependence of envelope inflation in massive stars
• Red Giants in the Small Magellanic Cloud. II. Metallicity Gradient and Age-Metallicity Relation
• Winds of low-metallicity OB-type stars: HST-COS spectroscopy in IC1613
• Spectroscopic evolution of massive stars on the main sequence
• BONNSAI: correlated stellar observables in Bayesian methods

Cited by in corpus (29)

• Constraining mixing in massive stars in the Small Magellanic Cloud
• Testing massive star evolution, star-formation history and feedback at low metallicity : Spectroscopic analysis of OB stars in the SMC Wing
• Variability of OB stars from TESS southern Sectors 1-13 and high-resolution IACOB and OWN spectroscopy
• Photometric detection of internal gravity waves in upper main-sequence stars. II. Combined TESS photometry and high-resolution spectroscopy
• X-Shooting ULLYSES: massive stars at low metallicity. I. Project Description
• Evolved Massive Stars at Low-metallicity I. A Source Catalog for the Small Magellanic Cloud
• The excess of cool supergiants from contemporary stellar evolution models defies the metallicity-independent Humphreys-Davidson limit
• X-Shooting ULLYSES: Massive stars at low metallicity. III. Terminal wind speeds of ULLYSES massive stars
• Recipes for bolometric corrections and Gaia luminosities of B-type stars: Application to an asteroseismic sample
• A dearth of young and bright massive stars in the Small Magellanic Cloud
• Inferring the presence of very massive stars in local star-forming regions
• Evolved Massive Stars at Low-metallicity III. A Source Catalog for the Large Magellanic Cloud
• Stripped-Envelope Stars in Different Metallicity Environments I. Evolutionary Phases, Classification and Populations
• Evolved Massive Stars at Low-metallicity II. Red Supergiant Stars in the Small Magellanic Cloud
• A high fraction of close massive binary stars at low metallicity
• Spectroscopic evolution of massive stars near the main sequence at low metallicity
• Reverse Algols and hydrogen-rich Wolf-Rayet stars from very massive binaries
• A systematic study of super-Eddington layers in the envelopes of massive stars
• A Panchromatic Study of Massive Stars in the Extremely Metal-Poor Local Group Dwarf Galaxy Leo A
• Populations of evolved massive binary stars in the Small Magellanic Cloud I: Predictions from detailed evolution models
• Mapping the core of the Tarantula Nebula with VLT-MUSE II. The spectroscopic Hertzsprung-Russell diagram of OB stars in NGC 2070
• Optically-thick Structure in Early B Type Supergiant Stellar Winds at Low Metallicities
• Flashlights: Prospects for constraining the Initial Mass Function around cosmic noon with caustic-crossing events
• The drastic impact of Eddington-limit induced mass ejections on massive star populations
• Strong Variability in AzV 493, an Extreme Oe-Type Star in the SMC
• New Field OB and OBe Binaries of the SMC Wing: Observational Properties and Population Modeling
• Micro-turbulence across the Hertzsprung-Russell diagram. Observational constrains for stars in the MW
• Kinematics of Wolf-Rayet Stars in the LMC: Clues to Subtype Origins
• BCD spectrophotometry for massive stars in transition phases