The IACOB project. VI. On the elusive detection of massive O-type stars close to the ZAMS

Abstract

The apparent lack of massive O-type stars near the zero-age main sequence (at ages < 2 Myr) is a topic widely discussed. Different explanations for this elusive detection have been proposed, but no firm conclusions have been reached yet. We reassess this empirical result benefiting from the high-quality spectroscopic observations of >400 Galactic O-type stars gathered by the IACOB and OWN surveys. We used temperatures and gravities from a iacob-gbat/fastwind spectroscopic analysis to locate our sample in the Kiel and spectroscopic HR diagrams. We evaluated the completeness of our sample of stars, observational biases using information from the Galactic O star catalog (GOSC), systematics of our methodology, and compare with other recent studies using smaller samples of Galactic O-type stars. We base our discussion on the spectroscopic HR diagram to avoid the use of uncertain distances. We performed a detailed study of the young cluster Trumpler-14 as an example of how Gaia cluster distances can help to construct the associated classical HR diagram. The apparent lack of massive O-type stars near the ZAMS with masses between 30 and 70 Msol persist even when spectroscopic results from a large, non-biased sample of stars are used. We do not find correlation between the dearth of stars and observational biases, limitations of our methodology, or the use of spectroscopic HR diagram instead of the classical one. Investigating the efficiency of mass accretion during the formation process we conclude that an adjustment of the accretion rate towards lower values could reconcile the hotter boundary of detected O-type stars and the theoretical birthline. Last, we discuss that the presence of a small sample of O2-O3.5 stars found closer to the ZAMS might be explained taking into account non-standard star evolution (e.g. binary interaction, mergers, or homogeneous evolution).

arXiv comment20 pages, 15 figures, accepted for publication in Astronomy & Astrophysics

References in corpus (97)

• Gaia Data Release 2. Summary of the contents and survey properties
• On the variation of the Initial Mass Function
• Binary interaction dominates the evolution of massive stars
• Gaia Data Release 2: The astrometric solution
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• Grids of stellar models with rotation - I. Models from 0.8 to 120 Msun at solar metallicity (Z = 0.014)
• A new calibration of stellar parameters of Galactic O stars
• Rotating Massive Main-Sequence Stars I: Grids of Evolutionary Models and Isochrones
• Gaia Data Release 2: using Gaia parallaxes
• Gaia Data Release 2: Catalogue validation
• The rotation rates of massive stars: the role of binary interaction through tides, mass transfer and mergers
• Atmospheric NLTE-Models for the Spectroscopic Analysis of Blue Stars with Winds. II. Line-Blanketed Models
• Evolution of Massive Protostars with High Accretion Rates
• The incidence of stellar mergers and mass gainers among massive stars
• Kinematics in Young Star Clusters and Associations with Gaia DR2
• UBVJHK synthetic photometry of Galactic O stars
• Quantitative Spectroscopy of O Stars at Low Metallicity. O Dwarfs in NGC 346
• The IACOB project: I. Rotational velocities in Northern Galactic O and early B-type stars revisited. The impact of other sources of line-broadening
• Circumventing the radiation pressure barrier in the formation of massive stars via disk accretion
• How mergers magnetise massive stars
• Formation of contact in massive close binaries
• Runaway stars as progenitors of supernovae and gamma-ray bursts
• Episodic accretion at early stages of evolution of low mass stars and brown dwarfs: a solution for the observed luminosity spread in HR diagrams?
• Evolution of Massive Protostars via Disk Accretion
• H II regions: Witnesses to massive star formation
• The MiMeS survey of magnetism in massive stars: Magnetic analysis of the O-type stars
• The Interplay of Magnetic Fields, Fragmentation and Ionization Feedback in High-Mass Star Formation
• Three-dimensional simulation of massive star formation in the disk accretion scenario
• Limiting Accretion onto Massive Stars by Fragmentation-Induced Starvation
• Gaia Data Release 2: The Celestial reference frame (Gaia-CRF2)
• Importance of the Initial Conditions for Star Formation - I. Cloud Evolution and Morphology
• A Census of the Carina Nebula. I: Cumulative Energy Input from Massive Stars
• Efficiency of mass transfer in massive close binaries, Tests from double-lined eclipsing binaries in the SMC
• Formation of massive stars by growing accretion rate
• The Galactic O-Star Spectroscopic Survey (GOSSS). III. 142 additional O-type systems
• The ages of young star clusters, massive blue stragglers and the upper mass limit of stars: analysing age dependent stellar mass functions
• Properties of Galactic early-type O-supergiants: A combined FUV-UV and optical analysis
• The spectroscopic Hertzsprung-Russell diagram
• The RMS Survey: Critical Tests of Accretion Models for the Formation of Massive Stars
• Observed luminosity spread in young clusters and Fu Ori stars: a unified picture
• The spectroscopic Hertzsprung-Russell diagram of Galactic massive stars
• On the Reliability of Stellar Ages and Age Spreads Inferred from Pre-Main Sequence Evolutionary Models
• The IACOB project: III. New observational clues to understand macroturbulent broadening in massive O- and B-type stars
• Understanding Spatial and Spectral Morphologies of Ultracompact H II Regions
• Structure and evolution of high-mass stellar mergers
• Neon Abundances in B-Stars of the Orion Association: Solving the Solar Model Problem?
• A new extragalactic distance determination method using the flux-weighted gravity of late B and early A supergiants
• Analysis of Galactic late-type O dwarfs: more constraints on the weak wind problem
• Properties of OB star-black hole systems derived from detailed binary evolution models
• The MiMeS Survey of Magnetism in Massive Stars: CNO surface abundances of Galactic O stars
• Massive stars at low metallicity: Evolution and surface abundances of O dwarfs in the SMC
• The VLT-FLAMES Tarantula Survey. XXIX. Massive star formation in the local 30 Doradus starburst
• The IACOB project. V. Spectroscopic parameters of the O-type stars in the modern grid of standards for spectral classification
• Forming spectroscopic massive proto-binaries by disk fragmentation
• The Massive Star Content of NGC 3603
• Magnetic field measurements of O stars with FORS1 at the VLT
• Importance of the Initial Conditions for Star Formation - III: Statistical Properties of Embedded Protostellar Clusters
• Spectroscopic and physical parameters of Galactic O-type stars. III. Mass discrepancy and rotational mixing
• Importance of the Initial Conditions for Star Formation - II. Fragmentation Induced Starvation and Accretion Shielding
• Nitrogen line spectroscopy in O-stars -- III. The earliest O-stars
• Distance and the Initial Mass Function of Young Open Clusters In The Eta Carina Nebula: Tr 14 and Tr 16
• Detection of a magnetic field on HD108: clues to extreme magnetic braking and the Of?p phenomenon
• Confirmation of the magnetic oblique rotator model for the Of?p star HD 191612
• Effects of close binary evolution on the main-sequence morphology of young star clusters
• A MAD view of Trumpler 14
• MONOS: Multiplicity Of Northern O-type Spectroscopic systems. I. Project description and spectral classifications and visual multiplicity of previously known objects
• Optical-NIR dust extinction towards Galactic O stars
• Evolution of stellar collision products in open clusters. I. Blue stragglers in N-body models of M67
• A Bake-Off Between CMFGEN and FASTWIND: Modeling the Physical Properties of SMC and LMC O-type Stars
• A CNO Dichotomy among O2 Giant Spectra in the Magellanic Clouds
• Exploring the origin of magnetic fields in massive stars: A survey of O-type stars in clusters and in the field
• The VLT-FLAMES Tarantula Survey XXVI: Properties of the O-dwarf population in 30 Doradus
• Orbital and physical properties of the $\sigma$ Ori Aa,Ab,B triple system
• The Ultraviolet Spectrum and Physical Properties of the Mass Donor Star in HD 226868 = Cygnus X-1
• High-resolution simulations of stellar collisions between equal-mass main-sequence stars in globular clusters
• Primordial Binary Evolution and Blue Stragglers
• The VLT-FLAMES Tarantula Survey. XIII: On the nature of O Vz stars in 30 Doradus
• A spectroscopic investigation of the O-type star population in four Cygnus OB associations. II. Determination of the fundamental parameters
• Gaia DR2 reveals a very massive runaway star ejected from R136
• Evidence for quasi-chemically homogeneous evolution of massive stars up to solar metallicity
• Massive star formation by accretion I. Disc accretion
• The non-thermal radio emitter HD 93250 resolved by long baseline interferometry
• Spectroscopic and physical parameters of Galactic O-type stars. II. Observational constraints on projected rotational and extra broadening velocities as a function of fundamental parameters and stellar evolution
• Massive stars in the hinterland of the young cluster, Westerlund 2
• The IACOB project: II. On the scatter of O-dwarf spectral type -- effective temperature calibrations
• Stellar models and isochrones from low-mass to massive stars including pre-main sequence phase with accretion
• A study of the effect of rotational mixing on massive stars evolution: surface abundances of Galactic O7-8 giant stars
• A Catalog of New Spectroscopically Confirmed Massive OB Stars in Carina
• Spectral classification and properties of the O Vz stars in the Galactic O-Star Spectroscopic Survey (GOSSS)
• The O star hinterland of the Galactic starburst, NGC 3603
• Gaia-ESO Survey: global properties of clusters Trumpler 14 and 16 in the Carina Nebula
• The distances to star-clusters hosting Red Supergiants: $\chi$ Per, NGC 7419, and Westerlund 1
• Chemical abundances of fast-rotating massive stars. I. Description of the methods and individual results
• Lucky Spectroscopy, an equivalent technique to Lucky Imaging. Spatially resolved spectroscopy of massive close visual binaries using the William Herschel Telescope
• Massive star formation by accretion II. Rotation: how to circumvent the angular momentum barrier?
• Accreting pre-main sequence models and abundance anomalies in globular clusters
• HST astrometry in the 30 Doradus region: II. Runaway stars from new proper motions in the Large Magellanic Cloud

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• Gaia-ESO Survey: massive stars in the Carina Nebula. II. The spectroscopic analysis of the O-star population
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