The effects of surface fossil magnetic fields on massive star evolution – II. Implementation of magnetic braking in mesa and implications for the evolution of surface rotation in OB stars

Abstract

The time evolution of angular momentum and surface rotation of massive stars is strongly influenced by fossil magnetic fields via magnetic braking. We present a new module containing a simple, comprehensive implementation of such a field at the surface of a massive star within the Modules for Experiments in Stellar Astrophysics (mesa) software instrument. We test two limiting scenarios for magnetic braking: distributing the angular momentum loss throughout the star in the first case, and restricting the angular momentum loss to a surface reservoir in the second case. We perform a systematic investigation of the rotational evolution using a grid of OB star models with surface magnetic fields (M = 5 − 60 M , Ω/Ω crit = 0.2 − 1.0, B p = 1 − 20 kG). We then employ a representative grid of B-type star models (M = 5, 10, 15 M , Ω/Ω crit = 0.2, 0.5, 0.8, B p = 1, 3, 10, 30 kG) to compare to the results of a recent selfconsistent analysis of the sample of known magnetic B-type stars. We infer that magnetic massive stars arrive at the zero age main sequence with a range of rotation rates, rather than with one common value. In particular, some stars are required to have close-to-critical rotation at the ZAMS. However, magnetic braking yields surface rotation rates converging to a common low value, making it difficult to infer the initial rotation rates of evolved, slowly-rotating stars.

On the origin of the bimodal rotational velocity distribution in stellar clusters: rotation on the pre-main sequence

“…Note that if fossil fields should survive until the pre-MS phase, magnetic coupling could be ensured for stars of any masses, although this would concern however a very small fraction of OB stars (only ∼ 7% have surface magnetic fields; e.g. Keszthelyi et al 2020 and references therein).…”

Asteroseismology of High-Mass Stars: New Insights of Stellar Interiors With Space Telescopes

“…Furthermore, based on dedicated studies, such as MiMeS (Wade et al, 2016), the BOB campaign (Morel et al, 2015), and the BRITE spectropolarimetric survey (Neiner et al, 2017), ∼10% of massive stars are inferred to host a large-scale magnetic field with polar field strengths that range from ∼100 G up to a few kG. The degeneracies within evolutionary models are also more complex when dealing with the presence of magnetic fields in massive stars (Alecian et al, 2014;Shultz et al, 2018;Keszthelyi et al, 2019Keszthelyi et al, , 2020.…”

Fundamental properties of a selected sample of Ap stars: Inferences from interferometric and asteroseismic constraints

“…Recent modelling approaches 4 using the mesa software instrument have accounted for two surface effects of fossil magnetic fields in massive star models (Keszthelyi et al 2019(Keszthelyi et al , 2020. These approaches rely on two long-term phenomena which result from the magnetospheric-wind interaction, namely, massloss quenching (which reduces the mass-loss rate of the star, e.g.…”

“…We use mesa r-12115 and modelling assumptions that are similar to those of Keszthelyi et al (2020). The initial abundances are adopted as Z ini = 0.014, Y ini = 0.266, X ini = 0.72, and the initial distribution of metals follows the description of Asplund et al (2009), with isotopic ratios adopted from Lodders (2003).…”

“…In addition to precise measurements of radii and luminosities, we assess the benefit of having seismic constraints, when available. In order to further strengthen the robustness of these results, we additionally use mesa software (Paxton et al 2011(Paxton et al , 2013(Paxton et al , 2015(Paxton et al , 2018(Paxton et al , 2019 where the effects of surface fossil magnetic fields have previously been implemented by Keszthelyi et al (2019Keszthelyi et al ( , 2020.…”