Atmospheric mass loss and stellar wind effects in young and old systems – II. Is TOI-942 the past of TOI-421 system?

Kubyshkina, Daria; Vidotto, A. A.; D’Angelo, Carolina Villarreal; Hazra, Gopal; Carleo, I.

doi:10.1093/mnras/stab3620

Cited by 8 publications

(5 citation statements)

References 59 publications

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“…Observed exoplanet samples typically do not allow to infer the past activity history of the host star, with the possible exception of some multi-planet systems (e.g. Kubyshkina et al 2019bKubyshkina et al ,a, 2022. Therefore, observed samples will typically have a spread of stellar activity histories, whose effect we described in the results section.…”

Section: Discussionmentioning

confidence: 99%

The influence of host star activity evolution on the population of super-Earths and mini-Neptunes

Ketzer¹,

Poppenhaeger²

2022

Preprint

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The detected exoplanet population displays a dearth of planets with sizes of about two Earth radii, the so-called radius gap. This is interpreted as an evolutionary effect driven by a variety of possible atmospheric mass loss processes of exoplanets. For mass loss driven by an exoplanet's irradiation by stellar X-ray and extreme-UV photons, the time evolution of the stellar magnetic activity is important. It is known from observations of open stellar clusters that stars of the same age and mass do not all follow the same time evolution of activity-induced X-ray and extreme-UV luminosities. Here we explore how a realistic spread of different stellar activity tracks influences the mass loss and radius evolution of a simulated population of small exoplanets and the observable properties of the radius gap. Our results show qualitatively that different saturation time scales, i.e. the young age at which stellar high-energy emission starts to decline, and different activity decay tracks over moderate stellar ages can cause changes in the population density of planets in the gap, as well as in the observable width of the gap. We also find that while the first 100 million years of mass loss are highly important to shape the radius gap, significant evolution of the gap properties is expected to take place for at least the first 500-600 million years, i.e. the age of the Hyades cluster. Observations of exoplanet populations with defined ages will be able to shed more light on the radius gap evolution.

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Section: Discussionmentioning

confidence: 99%

The influence of host star activity evolution on the population of super-Earths and mini-Neptunes

Ketzer¹,

Poppenhaeger²

2022

Preprint

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“…Koskinen et al Fig. 3 Evolution of planetary radii (solid lines and the left Y-axis) and atmospheric mass fractions (dash-dotted lines and the right Y-axis) with time for planets of different masses (colour-coded in the legend) evolving at ∼ 0.0909 AU orbit around a solar mass star, as predicted by atmospheric evolution models by Kubyshkina et al (2022b). The initial atmospheric mass fractions were set according to the approximation by Mordasini (2020) 2022; Huang et al 2023).…”

Section: Atmospheric Evolution: From Giant Planets To Super-earthsmentioning

confidence: 97%

“…The majority of recent studies (e.g. Baraffe et al 2004;Fortney and Nettelmann 2010;Lopez et al 2012;Lopez and Fortney 2014;Jin et al 2014;Mordasini et al 2015;Howe and Burrows 2015;Chen and Rogers 2016;Kubyshkina et al 2020Kubyshkina et al , 2022bEmsenhuber et al 2021;Gu and Chen 2023) tackle this problem by considering the hydrogen-dominated atmosphere on top of the inert solid core (which is typically assumed to be the mixture of silicates and metals but can have a more complex structure including ice/ocean layers; e.g. Valencia et al 2006;Dorn et al 2017;Venturini et al 2020).…”

Section: Atmospheric Evolution: From Giant Planets To Super-earthsmentioning

confidence: 99%

“…Therefore, it is considered the main driving mechanism of the atmospheric evolution (e.g. Murray-Clay et al 2009;Lopez et al 2012;Chen and Rogers 2016;Kubyshkina et al 2019bKubyshkina et al ,a, 2022bPezzotti et al 2021a;Gu and Chen 2023) and plays a major role in shaping the population of low to intermediate mass exoplanets as it is known to date (e.g. Fulton et al 2017;Fulton and Petigura 2018;Owen and Wu 2017;Gupta and Schlichting 2019;Mordasini 2020).…”

Section: Hydrodynamic Escapementioning

confidence: 99%

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Non-LTE effects in atmospheres of warm and hot Neptunes: implications for the atmospheric mass loss

Kubyshkina

Fossati²

2022

Preprint

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The warm- and hot-Neptune-type planets are known to experience significant atmospheric mass loss and are easier to observe and characterize in comparison to terrestrial-like planets. They represent, therefore, interesting targets in the context of planetary atmospheric evolution and star-planet interaction. The majority of studies, however, employ hydrodynamic simulations relying on simplified approaches in describing photoionization processes, or, on the other hand, use high-level photoionization solvers not accounting for dynamical effects. In this study, we aim to outline for which types of planets in the Neptune-like mass range the non-LTE effects become important (in particular - in terms of atmospheric mass loss) and to which extent the hydrodynamic effects (as adiabatic expansion) influence the theoretically predicted transmission spectra. To achieve this goal, we combine our 1D hydrodynamic upper atmosphere model (Kubyshkina et al., 2018) with the latest version of the non-LTE photoionization and radiative transfer code Cloudy (Ferland et al., 2017), which accounts for ionization and dissociation, atomic level transitions and chemical reactions for the lightest chemical elements up to zink. Thus, the former is responsible for resolving the hydrodynamic outflow and the latter solves the realistic photoionization and heating of the planetary atmosphere. We verify this scheme by comparing our results for a dozen of the high profile planets with the predictions of Salz et al., 2016, which use a similar approach. We apply this hybrid framework to model the upper atmospheres of a range of Neptune-like and terrestrial-like planets with masses between 1 and 50 Mearth, changing systematically the orbital parameters (and thus, equilibrium temperature), and the irradiation level from the host star. We find, that for the majority of warm and hot Neptunes, accounting for realistic non-LTE ionization/heating affects significantly the basic parameters of planetary atmospheres, predicting cooler, slower, and denser outflow compared to the predictions of the pure hydrodynamic model. The predictions of the hydrodynamic and hybrid models become closer at the highest levels of stellar radiation. In turn, accounting for hydrodynamic effects, in particular for expansion cooling, considerably affects the predictions of Cloudy models, and is therefore important for the interpretation of observations. &#160;

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“…In this study, we aim at quantifying the impact of atmospheric mass loss onto the observed MR distribution of planets across a wide range of masses. To this end, we employ an atmospheric evolution framework combining realistic hydrodynamic escape and planetary thermal evolution (Kubyshkina & Vidotto 2021;Kubyshkina et al 2022) applying it to a grid of planets in the 1-110 M ⊕ range on various orbits corresponding to planetary equilibrium temperatures (T eq ) not lower than 500 K (∼2.5-75 days). In particular, we aim at outlining the role played by the initial atmospheric parameters at formation and by atmospheric escape processes as a function of system parameters.…”

Section: Introductionmentioning

confidence: 99%

The mass-radius relation of intermediate-mass planets outlined by hydrodynamic escape and thermal evolution

Kubyshkina

Fossati

2022

A&A

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Context. Exoplanets in the mass range between Earth and Saturn show a large radius, and thus density, spread for a given mass. Aims. We aim at understanding to which extent the observed radius spread is affected by the specific planetary parameters at formation and by planetary atmospheric evolution, respectively. Methods. We employ planetary evolution modeling to reproduce the mass-radius (MR) distribution of the 198 so far detected planets with mass and radius measured to the ≤45% and ≤15% level, respectively, and less massive than 108 M ⊕ . We simultaneously account for atmospheric escape, based on the results of hydrodynamic simulations, and thermal evolution, based on planetary structure evolution models. Since the high-energy stellar radiation affects atmospheric evolution, we account for the entire range of possible stellar rotation evolution histories. To set the planetary parameters at formation, we use analytical approximations based on formation models. Finally, we build a grid of synthetic planets with parameters reflecting those of the observed distribution.Results. The predicted radius spread reproduces well the observed MR distribution, except for two distinct groups of outliers (≈10% of the population). The first group consists of very close-in Saturn-mass planets with Jupiter-like radii for which our modeling underpredicts the radius likely because it lacks additional (internal) heating similar to that responsible for inflation in hot Jupiters. The second group consists of warm (∼400-800 K) sub-Neptunes, which should host massive primordial hydrogen-dominated atmospheres, but instead present high densities indicative of small gaseous envelopes (<1-2%). This suggests that their formation, internal structure, and evolution is different from that of atmospheric evolution through escape of hydrogen-dominated envelopes accreted onto rocky cores. On average the observed characteristics of low-mass planets (≤10-15 M ⊕ ) strongly depend on the impact of atmospheric escape, and thus of the evolution of the host star's activity level, while primordial parameters are less relevant. Instead, for more massive planets, the parameters at formation play the dominant role in shaping the final MR distribution. In general, the intrinsic spread in the evolution of the activity of the host stars can explain just about a quarter of the observed radius spread.

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Atmospheric mass loss and stellar wind effects in young and old systems – II. Is TOI-942 the past of TOI-421 system?

Cited by 8 publications

References 59 publications

The influence of host star activity evolution on the population of super-Earths and mini-Neptunes

The influence of host star activity evolution on the population of super-Earths and mini-Neptunes

Non-LTE effects in atmospheres of warm and hot Neptunes: implications for the atmospheric mass loss

The mass-radius relation of intermediate-mass planets outlined by hydrodynamic escape and thermal evolution

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