Modules for Experiments in Stellar Astrophysics (MESA): Time-dependent Convection, Energy Conservation, Automatic Differentiation, and Infrastructure

Abstract

We update the capabilities of the open-knowledge software instrument Modules for Experiments in Stellar Astrophysics (MESA). The new auto_diff module implements automatic differentiation in MESA, an enabling capability that alleviates the need for hard-coded analytic expressions or finite-difference approximations. We significantly enhance the treatment of the growth and decay of convection in MESA with a new model for time-dependent convection, which is particularly important during late-stage nuclear burning in massive stars and electron-degenerate ignition events. We strengthen MESA’s implementation of the equation of state, and we quantify continued improvements to energy accounting and solver accuracy through a discussion of different energy equation features and enhancements. To improve the modeling of stars in MESA, we describe key updates to the treatment of stellar atmospheres, molecular opacities, Compton opacities, conductive opacities, element diffusion coefficients, and nuclear reaction rates. We introduce treatments of starspots, an important consideration for low-mass stars, and modifications for superadiabatic convection in radiation-dominated regions. We describe new approaches for increasing the efficiency of calculating monochromatic opacities and radiative levitation, and for increasing the efficiency of evolving the late stages of massive stars with a new operator-split nuclear burning mode. We close by discussing major updates to MESA’s software infrastructure that enhance source code development and community engagement.

Contamination in TESS Light Curves: The Case of the Fast Yellow Pulsating Supergiants

“…We thank the referee for their comments which improved the manuscript. (Paxton et al 2011(Paxton et al , 2013(Paxton et al , 2015(Paxton et al , 2018(Paxton et al , 2019Jermyn et al 2022).…”

“…For the construction of Figure 1 we computed nonrotating stellar evolution tracks for five different initial stellar masses (15 M e , 20 M e , 25 M e , 30 M e , and 35 M e ) using the stellar structure and evolution code MESA version 22.11.1 (Paxton et al 2011(Paxton et al , 2013(Paxton et al , 2015(Paxton et al , 2018(Paxton et al , 2019Jermyn et al 2022). The models were evolved from the Hayashi track to the end of core He burning, assuming an initial stellar mass fraction for hydrogen, helium, and metals of X = 0.7391, Y = 0.2562, and Z = 0.0047 for the LMC following Köhler et al 2015, who based these values on the observed abundances of young massive stars in the LMC (Brott et al 2011).…”

Nucleosynthesis of Binary-stripped Stars

“…This work builds on the work in Farmer et al (2021), which explored the chemical yields of 12 C, to extend the discussion to a larger set of isotopes (162) up to 64 Zn. We evolve a grid of single stars and binary-stripped stars using the MESA stellar evolution code (version 12115; Paxton et al 2011Paxton et al , 2013Paxton et al , 2015Paxton et al , 2018Paxton et al , 2019Jermyn et al 2023). These stars are evolved from the zero-age main sequence (MS) to CC and then through their SNe until shock breakout.…”

N-enhancement in GN-z11: First evidence for supermassive stars nucleosynthesis in proto-globular clusters-like conditions at high redshift?

“…To model nucleosynthesis in fastly growing SMS, we computed evolution models for 3 metallicities ([Fe/H]=-0.72, -1.14, and -2 dex, assuming [α/Fe]=+0.3 dex) with the stellar evolution code MESA (Paxton et al 2011(Paxton et al , 2013(Paxton et al , 2015(Paxton et al , 2018(Paxton et al , 2019Jermyn et al 2023). For a detailed description of our adopted stellar physics, we refer to Fragos et al (2023, their Sect.3).…”