The influence of metallicity on a combined stellar and disk evolution

Gehrig, Lukas; Steindl, T.; Vorobyov, Eduard I.; Guadarrama, Rodrigo; Zwintz, K.

doi:10.1051/0004-6361/202244408

Cited by 6 publications

(4 citation statements)

References 150 publications

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“…The vertical dotted line indicates the age estimate from Brewer et al (2023), and the gray shaded region represents the 1σ uncertainty on the age. The subsolar metallicity of ρ CrB results in an accelerated evolution of the star into the RGB (Gehrig et al 2023). The first peak in the stellar radius/luminosity at ∼11.6 Gyr corresponds to the helium flash and the transition into the horizontal branch (Bloecker 1995a(Bloecker , 1995b.…”

Section: Stellar Evolution Modelmentioning

confidence: 99%

Planetary Engulfment Prognosis within the ρ CrB System

Kane

2023

ApJ

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Exoplanets have been detected around stars at various stages of their lives, ranging from young stars emerging from formation to the latter stages of evolution, including white dwarfs and neutron stars. Post-main-sequence stellar evolution can result in dramatic, and occasionally traumatic, alterations to the planetary system architecture, such as tidal disruption of planets and engulfment by the host star. The ρ CrB system is a particularly interesting case of advanced main-sequence evolution, due to the relative late age and brightness of the host star, its similarity to solar properties, and the harboring of four known planets. Here, we use stellar evolution models to estimate the expected trajectory of the stellar properties of ρ CrB, especially over the coming 1.0–1.5 billion yr as it evolves off the main sequence. We show that the inner three planets (e, b, and c) are engulfed during the red giant phase and asymptotic giant branch, likely destroying those planets via either evaporation or tidal disruption at the fluid-body Roche limit. The outer planet, planet d, is briefly engulfed by the star several times toward the end of the asymptotic giant branch, but the stellar mass loss and subsequent changing planetary orbit may allow the survival of the planet into the white dwarf phase of the stellar evolution. We discuss the implications of this outcome for similar systems and describe the consequences for planets that may lie within the habitable zone of the system.

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Section: Stellar Evolution Modelmentioning

confidence: 99%

Planetary Engulfment Prognosis within the ρ CrB System

Kane

2023

ApJ

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“…Finally, stellar metallicity can affect the rotational evolution of the star during the pre-main sequence and the main sequence. Low-metallicity stars are expected to rotate faster compared to their solar-metallicity counterparts (e.g., Amard et al 2019;Gehrig et al 2023). As low-metallicity stars are more compact compared to solar metallicities, mechanisms that remove angular momentum from the star and scale with the stellar radius are less effective in a lowmetallicity environment during the Class II phase and beyond the main sequence (e.g., Gehrig et al 2023).…”

Section: Stellar Metallicitymentioning

confidence: 99%

“…Low-metallicity stars are expected to rotate faster compared to their solar-metallicity counterparts (e.g., Amard et al 2019;Gehrig et al 2023). As low-metallicity stars are more compact compared to solar metallicities, mechanisms that remove angular momentum from the star and scale with the stellar radius are less effective in a lowmetallicity environment during the Class II phase and beyond the main sequence (e.g., Gehrig et al 2023). In addition, the disk lifetime of low-metallicity stars is shorter compared to solar metallicities, and the pre-main sequence spinup due to contraction starts at an earlier age (Yasui et al 2016(Yasui et al , 2021Guarcello et al 2021;Gehrig et al 2023).…”

Section: Stellar Metallicitymentioning

confidence: 99%

“…As low-metallicity stars are more compact compared to solar metallicities, mechanisms that remove angular momentum from the star and scale with the stellar radius are less effective in a lowmetallicity environment during the Class II phase and beyond the main sequence (e.g., Gehrig et al 2023). In addition, the disk lifetime of low-metallicity stars is shorter compared to solar metallicities, and the pre-main sequence spinup due to contraction starts at an earlier age (Yasui et al 2016(Yasui et al , 2021Guarcello et al 2021;Gehrig et al 2023). We find similar results for the evolution during the first million years for a metallicity of Z = 0.1 Z (see Column b in Fig.…”

Section: Stellar Metallicitymentioning

confidence: 99%

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What governs the spin distribution of very young < 1 Myr low-mass stars

Gehrig¹,

Vorobyov²

2023

A&A

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Context. The origin of the stellar spin distribution at young ages is still unclear. Even in very young clusters (∼ 1 Myr), a significant spread is observed in rotational periods ranging from 1 to ∼ 10 days. Aims. We aim to study the parameters that might govern the spin distribution of low mass ( 1.0 M ) stars during the first million years of their evolution. Methods. We compute the evolution and rotational periods of young stars, using the MESA code, starting from a stellar seed, and take protostellar accretion, stellar winds, and the magnetic star-disk interaction into account. Furthermore, we add a certain fraction of the energy of accreted material into the stellar interior as additional heat and combine the resulting effects on stellar evolution with the stellar spin model. Results. For different combinations of parameters, stellar periods at an age of 1 Myr range between 0.6 days and 12.9 days. Thus, during the relatively short time period of 1 Myr, a significant amount of stellar angular momentum can already be removed by the interaction between the star and its accretion disk. The amount of additional heat added into the stellar interior, the accretion history, and the presence of disk and stellar winds have the strongest impact on the stellar spin evolution during the first million years. The slowest stellar rotations result from a combination of strong magnetic fields, a large amount of additional heat, and effective winds. The fastest rotators combine weak magnetic fields and ineffective winds or result from a small amount of additional heat added to the star. Scenarios that could lead to such configurations are discussed. Different initial rotation periods of the stellar seed, on the other hand, quickly converges and do not affect the stellar period at all. Conclusions. Our model matches up to 90% of the observed rotation periods in six young ( 3 Myr) clusters. Based on these intriguing results, we motivate to combine our model with a hydrodynamic disk evolution code to self-consistently include several important aspects such as episodic accretion events, magnetic disk winds, internal, and external photo-evaporation. Such a combined model could replace the widely-used disk-locking model during the lifetime of the accretion disk and provide valuable insights into the origin of the rotational period distribution of young clusters.

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Effects of accretion on the structure and rotation of forming stars

Amard,

Matt

2023

A&A

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Context. Rotation period measurements of low-mass stars show that the spin distributions in young clusters do not exhibit the spin-up expected due to contraction in the phase when a large fraction of stars is still surrounded by accretion discs. Many physical models have been developed to explain this feature based on different types of star-disc interactions alone. In this phase, the stars accrete mass and angular momentum and may experience accretion-enhanced magnetised winds. The stellar structure and angular momentum content thus strongly depend on the properties of the accretion mechanism. At the same time, the accretion of mass and energy has a significant impact on the evolution of the stellar structure and the moment of inertia. Our understanding of the spin rates of young stars therefore requires a description of how accretion affects the stellar structure and angular momentum simultaneously. Aims. We aim to understand the role of accretion to explain the observed rotation-rate distributions of forming stars. Methods. We computed evolution models of accreting very young stars and determined in a self-consistent way the effect of accretion on stellar structure and the angular momentum exchanges between the stars and their disc. We then varied the deuterium content, the accretion history, the entropy content of the accreted material, and the magnetic field as well as the efficiency of the accretion-enhanced winds. Results. The models are driven alternatively both by the evolution of the momentum of inertia and by the star-disc interaction torques. Of all the parameters we tested, the magnetic field strength, the accretion history, and the deuterium content have the largest impact. The injection of heat plays a major role only early in the evolution. Conclusions. This work demonstrates the importance of the moment of inertia evolution under the influence of accretion for explaining the constant rotation-rate distributions that are observed during the star-disc interactions. When we account for rotation, the models computed with the recently calculated torque along with a consistent structural evolution of the accreting star are able to explain the almost constant spin evolution for the whole range of parameters we investigated, but it only reproduces a narrow range around the median of the observed spin rate distributions. Further development, including for example more realistic accretion histories based on dedicated disc simulations, are likely needed to reproduce the extremes of the spin rate distributions.

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The influence of metallicity on a combined stellar and disk evolution

Cited by 6 publications

References 150 publications

Planetary Engulfment Prognosis within the ρ CrB System

Planetary Engulfment Prognosis within the ρ CrB System

What governs the spin distribution of very young < 1 Myr low-mass stars

Effects of accretion on the structure and rotation of forming stars

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