One obvious feature of the solar cycle is its variation from one cycle to another. In this article,
we review the dynamo models for the long-term variations of the solar cycle. By long-term …

The most widely accepted model of the solar cycle is the flux transport dynamo model. This
model evolved out of the traditional α Ω dynamo model which was first developed at a time …

Photochemistry is a fundamental process of planetary atmospheres that regulates the
atmospheric composition and stability. However, no unambiguous photochemical products …

Aims. We study the evolution of the rotation and the high energy X-ray, extreme ultraviolet
(EUV), and Ly-α emission for F, G, K, and M dwarfs, with masses between 0.1 and 1.2 M⊙ …

We report the detection of a transiting Earth-size planet around GJ 357, a nearby M2. 5 V
star, using data from the Transiting Exoplanet Survey Satellite (TESS). GJ 357 b (TOI …

Accurately measuring stellar parameters is a key goal to increase our understanding of the
observable Universe. However, current methods are limited by many factors, in particular …

Aims. The main objective of this project is to characterise chromospheric activity of FGK stars
from the HARPS archive. We start, in this first paper, by presenting a catalogue of …

We use the anelastic spherical harmonic code to model the convective dynamo of solar-type
stars. Based on a series of 15 3D MHD simulations spanning four bins in rotation and mass …

Context. One clear manifestation of dynamo action on the Sun is the 22-yr magnetic cycle,
exhibiting a polarity reversal and a periodic conversion between poloidal and toroidal fields …

Minimizing the impact of stellar variability in radial velocity (RV) measurements is a critical
challenge in achieving the 10 cm s− 1 precision needed to hunt for Earth twins. Since 2012 …