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The interaction of exoplanets with their host stars causes a vast diversity in bulk and atmospheric compositions, and physical and chemical conditions. Stellar radiation, especially at the shorter wavelengths, drives the chemistry in the…
Circumstellar disks are an essential ingredient of the formation of low-mass stars. It is unclear, however, whether the accretion-disk paradigm can also account for the formation of stars more massive than about 10 solar masses, in which…
We study a warping instability of a geometrically thin, non-self-gravitating, circumbinary disk around young binary stars on an eccentric orbit. Such a disk is subject to both the tidal torques due to a time-dependent binary potential and…
The temperature in most parts of a protoplanetary disk is determined by irradiation from the central star. Numerical experiments of Watanabe \& Lin (2008) suggested that such disks, also called `passive disks', suffer from a thermal…
The characterization of exoplanetary atmospheres has come of age in the last decade, as astronomical techniques now allow for albedos, chemical abundances, temperature profiles and maps, rotation periods and even wind speeds to be measured.…
Energetic particles, in the form of stellar energetic particles and cosmic rays, can lead to disequilibrium chemical effects in exoplanetary atmospheres. In Earth-like atmospheres, energetic particles can drive the formation of prebiotic…
All cool stars with outer convective zones have the potential to exhibit stochastically excited stellar oscillations. In this work, we explore the outer layers of stars less massive than the Sun. In particular, we have computed a set of…
Protostars and young stars are strongly spatially "clustered" or "correlated" within their natal giant molecular clouds (GMCs). We demonstrate that such clustering leads to the conclusion that the incident bolometric radiative flux upon a…
Star formation depends on the available gaseous "fuel" as well as galactic environment, with higher specific star formation rates where gas is predominantly molecular and where stellar (and dark matter) densities are higher. The partition…
Stars interact with their close-in planets through radiation, gravitation, and magnetic fields. We investigate the energy input to a planetary atmosphere by reconnection between stellar and planetary magnetic fields and compare it to the…
We present high-resolution zoom-in simulations of molecular clouds exposed to an interstellar radiation field and cosmic ray ionisation rate up to 1000 times stronger than that of the solar neighbourhood. We detail the evolution of the…
The strong X-ray irradiation from young solar-type stars may play a crucial role in the thermodynamics and chemistry of circumstellar discs, driving their evolution in the last stages of disc dispersal as well as shaping the atmospheres of…
X-rays and extreme ultraviolet radiation impacting on a gas produce a variety of effects that, depending on the electron content, may provide a significant heating of the illuminated region. In a planetary atmosphere of solar composition,…
Stars are not smooth. Their photosphere is covered by a granulation pattern associated with the heat transport by convection. The convection-related surface structures have different size, depth, and temporal variations with respect to the…
We explore the general astrobiological significance of F-type main-sequence stars with masses between 1.2 and 1.5 Msun. Special consideration is given to stellar evolutionary aspects due to nuclear main-sequence evolution. DNA is taken as a…
Radiation pressure can be dynamically important in star-forming environments such as ultra-luminous infrared and submillimeter galaxies. Whether and how radiation drives turbulence and bulk outflows in star formation sites is still unclear.…
We explore if carbon-based macromolecules (such as DNA) in the environments of stars other than the Sun are able to survive the effects of photospheric stellar radiation, such as UV-C. Therefore, we focus on main-sequence stars of spectral…
In this work we study the effect of disequilibrium processes on mixing ratio profiles of neutral species and on the simulated spectra of a hot Jupiter exoplanet that orbits stars of different spectral types. We also address the impact of…
Stellar high-energy radiation is a key driver of atmospheric erosion and evolution in exoplanets, directly affecting their long-term habitability. We present a comprehensive study on stellar high-energy radiation and its impact on…
High-energy irradiation of the circumstellar material might impact the structure and the composition of a protoplanetary disk and hence the process of planet formation. In this paper, we present a study on the possible influence of the…