A study of convective core overshooting as a function of stellar mass based on two-dimensional hydrodynamical simulations

Journal Article · Fri Jan 06 00:00:00 EST 2023 · Monthly Notices of the Royal Astronomical Society

DOI:https://doi.org/10.1093/mnras/stad009· OSTI ID:1909954

Baraffe, I.; Clarke, J.; Morison, A.; Vlaykov, D. G. ; Constantino, T.; Goffrey, T.; Guillet, T. ; Le Saux, A.; Pratt, J.

We perform two-dimensional (2D) numerical simulations of core convection for zero-age main-sequence stars covering a mass range from 3 to 20 M_⊙. The simulations are performed with the fully compressible time-implicit code music. We study the efficiency of overshooting, which describes the ballistic process of convective flows crossing a convective boundary, as a function of stellar mass and luminosity. We also study the impact of artificially increasing the stellar luminosity for 3 M_⊙ models. The simulations cover hundreds to thousands of convective turnover time-scales. Applying the framework of extreme plume events previously developed for convective envelopes, we derive overshooting lengths as a function of stellar masses. We find that the overshooting distance (d_ov) scales with the stellar luminosity (L) and the convective core radius (r_conv). We derive a scaling law d_ov ∝ L^1/3 r$$_{conv}^{1/2}$$, which is implemented in a one-dimensional stellar evolution code and the resulting stellar models are compared to observations. The scaling predicts values for the overshooting distance that significantly increase with stellar mass, in qualitative agreement with observations. Quantitatively, however, the predicted values are underestimated for masses ≳10 M_⊙. Our 2D simulations show the formation of a nearly adiabatic layer just above the Schwarzschild boundary of the convective core, as exhibited in recent three-dimensional simulations of convection. The most luminous models show a growth in size with time of the nearly adiabatic layer. This growth seems to slow down as the upper edge of the nearly adiabatic layer gets closer to the maximum overshooting length and as the simulation time exceeds the typical thermal diffusive time-scale in the overshooting layer.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA); European Research Council (ERC); Science and Technology Facilities Council (STFC)
• Grant/Contract Number: AC52-07NA27344; 787361-COBOM; ST/R000395/1; ST/K000373/1; ST/R002363/1; ST/R001014/1
• OSTI ID: 1909954
• Alternate ID(s): OSTI ID: 1971306
• Report Number(s): LLNL-JRNL-841720
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Vol. 519 Journal Issue: 4; ISSN 0035-8711
• Publisher: Oxford University Press
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
convection
hydrodynamics
stars
evolution