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
Z. Keszthelyi, G. Meynet, M. E. Shultz, A. David-Uraz, A. ud-Doula, R. H. D. Townsend, G. A. Wade, C. Georgy, V. Petit, S. P. Owocki
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 ($M_\star=5-60$ M$_\odot$, $Ω/Ω_{\rm crit} =0.2-1.0$, $B_{\rm p} =1-20$ kG). We then employ a representative grid of B-type star models ($M_\star=5, 10, 15$ M$_\odot$, $Ω/Ω_{\rm crit} =0.2 , 0.5, 0.8$, $B_{\rm p} = 1, 3 ,10, 30$ kG) to compare to the results of a recent self-consistent 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.
Two magnetic braking models are implemented in MESA for use in the MIST stellar model grids. Stars less than about 1.3 $M_{\odot}$ are observed to spin down over time through interaction with their magnetized stellar winds (i.e., magnetic braking). This is the basis for gyrochronology, and fundamental to the evolution of lower mass stars. The detailed physics behind magnetic braking are uncertain, as are 1D stellar evolution models. Thus, we calibrate our models and compare to data from open clusters. Each braking model tested here is capable of reproducing the data, albeit with some important…
Surface magnetic fields have a strong impact on stellar mass loss and rotation and, as a consequence, on the evolution of massive stars. In this work we study the influence of an evolving dipolar surface fossil magnetic field with an initial field strength of 4 kG on the characteristics of 15 M$_{\odot}$ solar metallicity models using the Geneva stellar evolution code. Non-rotating and rotating models considering two different scenarios for internal angular momentum transport are computed, including magnetic field evolution, mass-loss quenching, and magnetic braking. Magnetic field evolution r…
Sco X-1 is a low-mass X-ray binary (LMXB) that has one of the most precisely determined set of binary parameters such as the mass accretion rate, companions mass ratio and the orbital period. For this system, as well as for a large fraction of other well-studied LMXBs, the observationally-inferred mass accretion rate is known to strongly exceed the theoretically expected mass transfer rate. We suggest that this discrepancy can be solved by applying a modified magnetic braking prescription, which accounts for increased wind mass loss in evolved stars compared to main sequence stars. Using our m…
Magnetic fields can drastically change predictions of evolutionary models of massive stars via mass-loss quenching, magnetic braking, and efficient angular momentum transport, which we aim to quantify in this work. We use the MESA software instrument to compute an extensive main-sequence grid of stellar structure and evolution models, as well as isochrones, accounting for the effects attributed to a surface fossil magnetic field. The grid is densely populated in initial mass (3-60 M$_\odot$), surface equatorial magnetic field strength (0-50 kG), and metallicity (representative of the Solar nei…
Extremely low-mass white dwarfs (ELM WDs) are the result of binary evolution in which a low-mass donor star is stripped by its companion leaving behind a helium-core white dwarf. We explore the formation of ELM WDs in binary systems considering the Convection And Rotation Boosted magnetic braking treatment. Our evolutionary sequences were calculated using the MESA code, with initial masses of 1.0 and 1.2 Msun (donor), and 1.4 (accretor), compatible with low mass X-ray binaries (LMXB) systems. We obtain ELM models in the range 0.15 to 0.27 Msun from a broad range of initial orbital periods, 1 t…
A modest change in magnetic braking at the fully convective boundary explains cataclysmic variable evolution
Universidad Técnica Federico Santa María (UTFSM)（费德里科·圣玛丽亚技术大学）；Pontificia Universidad Católica de Valparaíso (PUCV)（瓦尔帕莱索天主教 Pontificia 大学）；University of Sheffield（谢菲尔德大学）；Yunnan Observatories, CAS（中国科学院云南天文台）；Leibniz-Institut für Astrophysik Potsdam (AIP)（波茨坦阿基米德天体物理研究所）
Evolution of cataclysmic variables under different magnetic braking prescriptions
School of Physical Science and Technology, Xinjiang University（新疆大学物理科学与技术学院）；Department of Nuclear Physics and Astronomy, Institute of Engineering Physics, Samarkand State University（撒马尔罕国立大学工程物理学院核物理与天文学系）
Magnetic configurations, stable on the long term, appear to exist in various evolutionary phases, from Main-Sequence stars to white dwarfs and neutron stars. The large scale ordered nature of these fields, often approximately dipolar, and their scaling according to the flux conservation scenario favor the model of a fossil field (Duez et al. 2010). We make some first estimates of the magnetic coupling between the stellar cores and the outer layers in red giants and supergiants. Analytical expressions of the truncation radius of the field coupling are established for a convective envelope and f…
We present a new method for constraining the mass transfer evolution of low mass X-ray binaries (LMXBs) - a reverse population synthesis technique. This is done using the detailed 1D stellar evolution code MESA (Modules for Experiments in Stellar Astrophysics) to evolve a high-resolution grid of binary systems spanning a comprehensive range of initial donor masses and orbital periods. We use the recently developed Convection And Rotation Boosted (CARB) magnetic braking scheme. The CARB magnetic braking scheme is the only magnetic braking prescription capable of reproducing an entire sample of …
Black widows are millisecond pulsars with low-mass companions, a few per cent the mass of the sun, on orbits of several hours. These companions are presumably the remnants of main sequence stars that lost their mass through a combination of Roche-lobe overflow and ablation by the host pulsar's high-energy radiation. While ablation itself is too weak to significantly reduce the mass of the companion star, the ablated wind couples to its magnetic field, removes orbital angular momentum, and thus maintains stable Roche-lobe overflow. We use the MESA stellar evolution code, complemented by analyti…
Observational and theoretical work has now established that the fossil fields of magnetic massive stars are surviving remnants from an earlier event, or an earlier evolutionary phase. However, many important questions remain regarding the effects of these fields on the late stages of stellar evolution, as well as their impact on the core-collapse mechanism and the formation of exotic compact objects such as magnetars and gravitational wave progenitors. There is currently a critical need to incorporate the impact of fossil fields in models of the structure and evolution of magnetic stars, and t…
$τ$ Sco, a well-studied magnetic B-type star in the Upper Sco association, has a number of surprising characteristics. It rotates very slowly and shows nitrogen excess. Its surface magnetic field is much more complex than a purely dipolar configuration which is unusual for a magnetic massive star. We employ the CMFGEN radiative transfer code to determine the fundamental parameters and surface CNO and helium abundances. Then, we employ MESA and GENEC stellar evolution models accounting for the effects of surface magnetic fields. To reconcile $τ$ Sco's properties with single-star models, an incr…
It is generally believed that Ultracompact X-ray binaries (UCXBs) evolved from binaries consisting of a neutron star accreting from a low-mass white dwarf or helium star where mass transfer is driven by gravitational radiation. However, the standard white-dwarf evolutionary channel cannot produce the relatively long-period ($40 - 60$\,min) UCXBs with high time-averaged mass-transfer rate. In this work, we explore an alternative evolutionary route toward UCXBs where the companions evolve from intermediate-mass Ap/Bp stars with an anomalously strong magnetic field ($100 - 10000$\,G). Including t…
Large-scale dipolar surface magnetic fields have been detected in a fraction of OB stars, however only few stellar evolution models of massive stars have considered the impact of these fossil fields. We are performing 1D hydrodynamical model calculations taking into account evolutionary consequences of the magnetospheric-wind interactions in a simplified parametric way. Two effects are considered: i) the global mass-loss rates are reduced due to mass-loss quenching, and ii) the surface angular momentum loss is enhanced due to magnetic braking. As a result of the magnetic mass-loss quenching, t…
Magnetism can greatly impact the evolution of stars. In some stars with OBA spectral types there is direct evidence via the Zeeman effect for stable, large-scale magnetospheres, which lead to the spin-down of the stellar surface and reduced mass loss. So far, a comprehensive grid of stellar structure and evolution models accounting for these effects was lacking. For this reason, we computed and studied models with two magnetic braking and two chemical mixing schemes in three metallicity environments with the MESA software instrument. We find notable differences between the subgrids, which affe…
How plasma coupling and convective-zone depth shape the rotation of solar-mass stars
Instituto Superior de Gestão（高等管理学院）；Centro de Astrofísica e Gravitação - CENTRA, Departamento de Física, Instituto Superior Técnico IST, Universidade de Lisboa - UL（里斯本大学高等理工学院物理系天体物理学与引力中心）；Atlântica – Instituto Universitário（大西洋大学学院）
We investigate the surface nitrogen content of the six magnetic O stars known to date as well as of the early B-type star tau Sco. We compare these abundances to predictions of evolutionary models to isolate the effects of magnetic field on the transport of elements in stellar interiors. We conduct a quantitative spectroscopic analysis of the sample stars with state-of-the-art atmosphere models. We rely on high signal-to-noise ratio, high resolution optical spectra obtained with ESPADONS at CFHT and NARVAL at TBL. Atmosphere models and synthetic spectra are computed with the code CMFGEN. Value…
Near-core magnetic field strengths inferred from gravity modes in intermediate-mass stars
DTU Space, Technical University of Denmark（丹麦技术大学空间中心）；Department of Engineering Sciences and Applied Mathematics, Northwestern University（西北大学工程科学与应用数学系）；CIERA, Northwestern University（西北大学天体物理中心与地球资源观测与应用研究）；Department of Applied Mathematics, School of Mathematics, University of Leeds（利兹大学数学学院应用数学系）；LIRA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université（巴黎天文台拉格朗日天体物理学实验室）
