Accretion, winds and outflows in young stars

Günther, H. M.

doi:10.1002/asna.201211770

Cited by 15 publications

(12 citation statements)

References 75 publications

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“…The physical motivation for an inner edge is a magnetospheric cavity (Bouvier et al 2007), where ionized material of the disk is lifted by the magnetic field lines from the midplane and accreted onto the star. This typically happens at the corotation radius (e.g., Günther 2013), where the magnetic field rotates at the same speed as the gas. It is therefore reasonable to not extend the modeled disk closer to the star than its corotation radius.…”

Section: Inner Edgementioning

confidence: 99%

The New Generation Planetary Population Synthesis (NGPPS)

Burn

Schlecker

Mordasini

et al. 2021

A&A

134

119

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Context. Previous theoretical works on planet formation around low-mass stars have often been limited to large planets and individual systems. As current surveys routinely detect planets down to terrestrial size in these systems, models have shifted toward a more holistic approach that reflects their diverse architectures. Aims. Here, we investigate planet formation around low-mass stars and identify differences in the statistical distribution of modeled planets. We compare the synthetic planet populations to observed exoplanets and we discuss the identified trends. Methods. We used the Generation III Bern global model of planet formation and evolution to calculate synthetic populations, while varying the central star from Solar-like stars to ultra-late M dwarfs. This model includes planetary migration, N-body interactions between embryos, accretion of planetesimals and gas, and the long-term contraction and loss of the gaseous atmospheres. Results. We find that temperate, Earth-sized planets are most frequent around early M dwarfs (0.3 M⊙–0.5 M⊙) and that they are more rare for Solar-type stars and late M dwarfs. The planetary mass distribution does not linearly scale with the disk mass. The reason behind this is attributed to the emergence of giant planets for M⋆ ≥ 0.5 M⊙, which leads to the ejection of smaller planets. Given a linear scaling of the disk mass with stellar mass, the formation of Earth-like planets is limited by the available amount of solids for ultra-late M dwarfs. For M⋆ ≥ 0.3 M⊙, however, there is sufficient mass in the majority of systems, leading to a similar amount of Exo-Earths going from M to G dwarfs. In contrast, the number of super-Earths and larger planets increases monotonically with stellar mass. We further identify a regime of disk parameters that reproduces observed M-dwarf systems such as TRAPPIST-1. However, giant planets around late M dwarfs, such as GJ 3512b, only form when type I migration is substantially reduced. Conclusions. We are able to quantify the stellar mass dependence of multi-planet systems using global simulations of planet formation and evolution. The results fare well in comparison to current observational data and predict trends that can be tested with future observations.

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Section: Inner Edgementioning

confidence: 99%

The New Generation Planetary Population Synthesis (NGPPS)

Burn

Schlecker

Mordasini

et al. 2021

A&A

134

119

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“…Inner disk edge R in The physical motivation for an inner edge of the gas disk is the development of a magnetospheric cavity (Bouvier et al 2007), which is thought to extend to the corotation radius, i.e. the location where the angular velocity of the stellar magnetic field and of the orbiting gas are equal (e.g., Günther 2013). For the numerical disk, we adopted the orbit radius corresponding to the rotation period of its host star for R in .…”

Section: Dust-to-gas Ratio ζ Dgmentioning

confidence: 99%

The New Generation Planetary Population Synthesis (NGPPS). III. Warm super-Earths and cold Jupiters: A weak occurrence correlation, but with a strong architecture-composition link

Schlecker,

Mordasini,

Emsenhuber

et al. 2020

Preprint

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Context. Recent observational findings have suggested a positive correlation between the occurrence rates of inner super-Earths and outer giant planets. These results raise the question if the trend can be reproduced and explained by planet formation theory. Aims. Here, we investigate the properties of inner super-Earths and outer giant planets that form according to the core accretion picture. The aim of this research was to study mutual relations between these planet species in synthetic planet populations and to compare them to the observed exoplanet population. Methods. We invoke the Generation 3 Bern model of planet formation and evolution to simulate 1000 multi-planet systems. We then confront these synthetic systems with the observed sample, taking into account the detection bias that distorts the observed demographics.Results. The formation of warm super-Earths and cold Jupiters in the same system is enhanced compared to the individual appearances, albeit weaker than proposed by observations. We attribute the discrepancy to dynamically active giant planets, which frequently disrupt inner super-Earth systems in the synthetic population. This result could be interpreted as an overestimation of the migration rates predicted by giant planet migration theory. We further find differences in the volatile content of planets in different system architectures and predict that high-density super-Earths are more likely to host an outer giant. This correlation can be tested observationally. Finally, super-Earth occurrence shows a negative correlation with metallicity in giant-hosting systems. The reason for this is that giant planets around high-metallicity stars are frequently dynamically active, which poses a threat to inner planetary systems.

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“…The dominant timescale in the optical is the stellar rotation period, typically a few days to a week or more (Rydgren & Vrba 1983;Bouvier et al 1986;Nguyen et al 2009). YSOs can have cool spots caused by magnetic activity similar to our Sun and also hot spots which mark the impact points of the accretion funnels onto the stellar surface (see, e.g., review by Günther 2013). This impact happens at freefall velocities up to 500 km s −1 ; thus, the accretion shock heats the accreted mass to X-ray emitting temperatures (see, e.g., reviews by Güdel 2004;Günther 2011).…”

Section: Ormentioning

confidence: 99%

“…YSOs can have cool spots caused by magnetic activity similar to our Sun and also hot spots which mark the impact points of the accretion funnels onto the stellar surface (see, e.g., review by Günther 2013). This impact happens at freefall velocities up to 500 km s −1 ; thus, the accretion shock heats the accreted mass to X-ray emitting temperatures (see, e.g., reviews by Güdel 2004;Günther 2011). In the optical, the accretion region appears as emission that often is approximated as a blackbody with temperature T < 10 000 K (Calvet & Gullbring 1998;Ingleby et al 2012, but see also Dodin & Lamzin 2012 who argue that line emission contributes to the veiling in addition to a continuum).…”

Section: Ormentioning

confidence: 99%

Ysovar: Mid-Infrared Variability in the Star-Forming Region Lynds 1688

Günther

Cody

Covey

et al. 2014

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The emission from young stellar objects (YSOs) in the mid-IR is dominated by the inner rim of their circumstellar disks. We present an IR-monitoring survey of ∼ 800 objects in the direction of the Lynds 1688 (L1688) star forming region over four visibility windows spanning 1.6 years using the Spitzer space telescope in its warm mission phase. Among all lightcurves, 57 sources are cluster members identified based on their spectral-energy distribution and X-ray emission. Almost all cluster members show significant variability. The amplitude of the variability is larger in more embedded YSOs. Ten out of 57 cluster members have periodic variations in the lightcurves with periods typically between three and seven days, but even for those sources, significant variability in addition to the periodic signal can be seen. No period is stable over 1.6 years. Non-periodic lightcurves often still show a preferred timescale of variability which is longer for more embedded sources. About half of all sources exhibit redder colors in a fainter state. This is compatible with time-variable absorption towards the YSO. The other half becomes bluer when fainter. These colors can only be explained with significant changes in the structure of the inner disk. No relation between mid-IR variability and stellar effective temperature or X-ray spectrum is found.

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Accretion, winds and outflows in young stars

Cited by 15 publications

References 75 publications

The New Generation Planetary Population Synthesis (NGPPS)

The New Generation Planetary Population Synthesis (NGPPS)

The New Generation Planetary Population Synthesis (NGPPS). III. Warm super-Earths and cold Jupiters: A weak occurrence correlation, but with a strong architecture-composition link

Ysovar: Mid-Infrared Variability in the Star-Forming Region Lynds 1688

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