Analyzing protostellar evolution using MESA to understand the survival of fossil magnetic fields.
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Date
2025
Journal Title
Journal ISSN
Volume Title
Publisher
Universidad de Concepción
Abstract
La observación de campos magnéticos fósiles en estrellas radiativas, ha llevado al desarrollo de diferentes teorías sobre su origen. Entre ellas, la teoría de campos fósiles es un posible explicación. Sin embargo, la supervivencia de tales campos depende intrínsecamente de la estructura estelar. Nuestra meta es obtener la masa típica de la protoestrella para el cual ocurre la transición desde un estado convectivo hasta uno radiativo, ya que esto favorece fuertemente la supervivencia de estos campos magnéticos. Estudiamos la evolución en la fase de pre-main sequence en protoestrellas de masa intermedia usando los Modules for Experiments in Stellar Astrophysics (MESA), un código de evolución estelar en 1D, investigando la dependencia en la metalicidad y la tasa de acreción media, considerando diferentes escenarios. Encontramos que la transición ocurre generalmente entre ∼ 1.3 M⊙ y ∼ 2.8 M⊙ para todos los modelos estudiados y explica naturalmente que es más probable que los campos magnéticos sobrevivan en estrellas con mayor masa, como también fue encontrado en observaciones. A menor metalicidad, la transición ocurre a masas más bajas. Sin embargo, en modelos con altas tasas de acreción, los campos magnéticos acretados podrían disiparse en las capas convectivas externas. El modelo predice que la fracción de estrellas radiativas con campos magnéticos intensos debería aumentar por debajo de Z = 0.01.
The observation of strong magnetic fields in radiative stars has led to the development of diferent theories about their origin. Among them, the fossil field theory offers a possible explanation. However, the survival of such fields is intrinsically dependent on the stellar structure. Our goal is to derive the typical mass of protostars for which the transition from a convective to a radiative state occurs, as the latter will strongly favor the possible survival of magnetic fields. We study the pre-main-sequence evolution of intermediate-mass protostars using the Modules for Experiments in Stellar Astrophysics (MESA), a 1D stellar evolution code, investigating the dependence on metallicity and average accretion rate, considering different accretion scenarios. We find that the transition generally occurs between ∼ 1.3 M⊙ and ∼ 2.8 M⊙ for all the models studied here and it naturally explains that it is more likely that magnetic fields will survive in more massive stars, as also found in observations. At lower metallicity, this transition is found to happen at a lower mass. However, in models with high accretion rates, any accreted magnetic fields could still be dissipated in the outer convective layers. An additional prediction of our model is that the fraction of radiative stars with strong magnetic fields should increase below metallicities of Z = 0.01.
The observation of strong magnetic fields in radiative stars has led to the development of diferent theories about their origin. Among them, the fossil field theory offers a possible explanation. However, the survival of such fields is intrinsically dependent on the stellar structure. Our goal is to derive the typical mass of protostars for which the transition from a convective to a radiative state occurs, as the latter will strongly favor the possible survival of magnetic fields. We study the pre-main-sequence evolution of intermediate-mass protostars using the Modules for Experiments in Stellar Astrophysics (MESA), a 1D stellar evolution code, investigating the dependence on metallicity and average accretion rate, considering different accretion scenarios. We find that the transition generally occurs between ∼ 1.3 M⊙ and ∼ 2.8 M⊙ for all the models studied here and it naturally explains that it is more likely that magnetic fields will survive in more massive stars, as also found in observations. At lower metallicity, this transition is found to happen at a lower mass. However, in models with high accretion rates, any accreted magnetic fields could still be dissipated in the outer convective layers. An additional prediction of our model is that the fraction of radiative stars with strong magnetic fields should increase below metallicities of Z = 0.01.
Description
Tesis presentada para optar al grado de Magíster en Astronomía.
Keywords
Stars, Magnetic fields, Stars Formation, Astrophysics