The ESO UVES/FEROS Large Programs of TESS OB pulsators. II. On the physical origin of macroturbulence

Abstract

Spectral lines of hot massive stars are known to exhibit large excess broadening in addition to rotational broadening. This excess broadening is often attributed to macroturbulence whose physical origin is a matter of active debate in the stellar astrophysics community. By looking into the statistical properties of a large sample of O- and B-type stars, both in the Galaxy and LMC, we aim to shed light on the physical origin of macroturbulent line broadening. We deliver newly measured macroturbulent velocities for 86 stars from the Galaxy in a consistent manner with 126 stars from the LMC. A total sample of 594 O- and B-type stars with measured macroturbulent velocities was composed by complementing our sample with archival data. Furthermore, we compute an extensive grid of MESA models to compare, in a statistical manner, the predicted interior properties of stars (such as convection and wave propagation) with the inference of macroturbulent velocities from high-resolution spectroscopic observations. We find the presence of two principally different regimes where, depending on the initial stellar mass, different mechanisms may be responsible for the observed excess line broadening. Stars with initial masses above some 30$M_{\odot }$ are found to have macroturbulent velocities fully determined by subsurface convective zones formed in the iron opacity bump (FeCZ), while some other mechanism is required to explain observations for masses below 12$M_{\odot }$. The latter finding leaves the potential for waves generated at the interface of the convective core and radiative envelope of the star to be responsible for the observed macroturbulent broadening. Both mechanisms may co-exist in the intermediate regime of stellar masses, between some 12 and 30$M_{\odot }$.

Accepted for publication in A&A on 17 Oct 2024

References in corpus (25)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
• Modules for Experiments in Stellar Astrophysics (MESA): Time-Dependent Convection, Energy Conservation, Automatic Differentiation, and Infrastructure
• CERES: A Set of Automated Routines for Echelle Spectra
• Low-frequency gravity waves in blue supergiants revealed by high-precision space photometry
• The spectroscopic Hertzsprung-Russell diagram
• The IACOB project: III. New observational clues to understand macroturbulent broadening in massive O- and B-type stars
• Variability of OB stars from TESS southern Sectors 1-13 and high-resolution IACOB and OWN spectroscopy
• Three-Dimensional Simulations of Massive Stars: I. Wave Generation and Propagation
• Photometric detection of internal gravity waves in upper main-sequence stars. II. Combined TESS photometry and high-resolution spectroscopy
• On the use of the Fourier Transform to determine the projected rotational velocity of line-profile variable B stars
• Low-frequency variability in massive stars: Core generation or surface phenomenon?
• The IACOB project. VI. On the elusive detection of massive O-type stars close to the ZAMS
• Stochastic Low Frequency Variability in 3-Dimensional Radiation Hydrodynamical Models of Massive Star Envelopes
• Two-Dimensional Simulations of Internal Gravity Waves in The Radiation Zones of Intermediate-Mass Stars
• The photometric variability of massive stars due to gravity waves excited by core convection
• Astrophysical properties of 15062 Gaia DR3 gravity-mode pulsators: pulsation amplitudes, rotation, and spectral line broadening
• Surface Manifestation of Stochastically Excited Internal Gravity Waves
• Metallicity dependence of turbulent pressure and macroturbulence in stellar envelopes
• Internal Gravity Waves in Massive Stars II: Frequency Analysis Across Stellar Mass
• Turbulence Supported Massive Star Envelopes
• Analysis of high-resolution FEROS spectroscopy for a sample of variable B-type stars assembled from TESS photometry
• Three-Dimensional Simulations of Massive Stars: II. Age Dependence
• Synthesizing Spectra from 3D Radiation Hydrodynamic Models of Massive Stars Using Monte Carlo Radiation Transport
• The ESO UVES/FEROS Large Programs of TESS OB pulsators. I. Global stellar parameters from high-resolution spectroscopy

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