Stellar rotation and its connection to the evolution of hydrogen-dominated atmospheres of exoplanets

TL;DR

This paper investigates how the diverse rotational evolution of host stars influences the atmospheric mass loss of exoplanets, affecting their observed densities and evolutionary outcomes.

Contribution

It analyzes the impact of stellar rotation history variability on planetary atmospheric escape and exoplanet population diversity.

Findings

Stellar rotation history significantly affects planetary atmospheric mass loss.

Variations in initial stellar rotation rates lead to diverse planetary evolution paths.

The non-uniqueness of stellar rotation evolution introduces uncertainties in exoplanet population models.

Abstract

The population of known low- to intermediate-mass exoplanets shows a large spread in densities, which is believed to be due to the diversity of planetary atmospheres and thus controlled by planetary atmospheric mass loss. One of the main drivers of long-term atmospheric escape is the absorption of high-energy XUV radiation from the host star. For main sequence solar-like stars, rotation and XUV radiation are closely connected, with faster rotating stars being XUV brighter and with both rotation and XUV decreasing with time. This evolution, however, does not follow a unique path, as stars born with the same mass and metallicity can have widely different initial rotation rates. This non-uniqueness holds up to about 1 Gyr, while atmospheric escape from exoplanets is strongest. The atmospheric mass loss through this period is often deciding the future of the planet and its position in the observed population. Therefore, the diversity of possible stellar histories can be an uncertain factor affecting the predictions of population studies. Here, I explore its relevance for different planets and different host stars.