Related papers: Assessing the capability of a model-based stellar …
Recently nonthermal radio transients from the quiet sun have been discovered and it has been hypothesised using rough calculations that they might be important for coronal heating. It is well realized that energy calculations using coherent…
The interactions between stars and their orbiting planets, driven by forces such as stellar radiation and gravity, play an essential role in shaping exoplanetary atmospheres and gas-rich debris discs. One way to look into the composition of…
Photospheric radius expansion during X-ray bursts can be used to measure neutron star radii and help constrain the equation of state of neutron star matter. Understanding the stellar wind dynamics is important for interpreting observations.…
Spectroscopic analyses with the intention of the interpretation of the UV-spectra of the brightest stars as individuals - supernovae - or as components of star-forming regions - massive O stars - provide a powerful tool with great…
Anomalies in the abundance measurements of short lived radionuclides in meteorites indicate that the protosolar nebulae was irradiated by a large number of energetic particles ($E\gtrsim10\,$MeV), often called solar cosmic rays. The…
The chemical evolution of an exoplanetary Venus-like atmosphere is dependent upon the ultraviolet to near ultraviolet (FUV-NUV) radiation ratio from the parent star, the balance between CO$_{2}$ photolysis and recombination via reactions…
The formation of low-mass stars in molecular clouds involves accretion disks and jets, which are of broad astrophysical interest. Accreting stars represent the closest examples of these phenomena. Star and planet formation are also…
The upcoming deployment of JWST will dramatically advance our ability to characterize exoplanet atmospheres, both in terms of precision and sensitivity to smaller and cooler planets. Disequilibrium chemical processes dominate these cooler…
The young magnetically active solar-like stars are efficient generators of ionizing radiation in the form of X-ray and Extreme UV (EUV) flux, stellar wind and eruptive events. These outputs are the critical factors affecting atmospheric…
Existing stellar X-ray surveys suggest major problems in our understanding of the evolution of stellar magnetic activity in solar and late-type stars, reaching conflicting conclusions over the rate of decay of X-ray activity and the…
The achievable level of precision on photospheric abundances of stars is a major limiting factor on investigations of exoplanet host star characteristics, the chemical histories of star clusters, and the evolution of the Milky Way and other…
We address the question how accurately stellar ages can be determined by stellar evolution theory. We select the star with the best observational material available - our Sun. We determine the solar age by fitting solar evolution models to…
For solar-system objects, ultraviolet spectroscopy has been critical in identifying sources for stratospheric heating and measuring the abundances of a variety of hydrocarbon and sulfur-bearing species, produced via photochemical…
The Atmospheric Imaging Assembly (AIA) and the Exteme-ultraviolet Variability Experiment (EVE) onboard the Solar Dynamics Observatory include spectral windows in the X-ray/EUV band. Accuracy and completeness of the atomic data in this…
We present preliminary results on the calculation of synthetic spectra obtained with the stellar model atmospheres developed by Cardona, Crivellari, and Simonneau. These new models have been used as input within the SYNTHE series of codes…
Planet formation takes place in protoplanetary discs around young T-Tauri stars. PDS 70 is one of the first confirmed examples of a system where the planets are currently forming in gaps in the disc, and can be directly imaged. One of the…
Solar flares effectively accelerate particles to non-thermal energies. These accelerated electrons are responsible for energy transport and subsequent emissions in HXR, radio, and UV/EUV radiation. Due to the steeply decreasing electron…
The detection of excess of soft X-ray or Extreme Ultraviolet (EUV) radiation, above the thermal contribution from the hot intracluster medium (ICM), has been a controversial subject ever since the initial discovery of this phenomenon. We…
Spectra of late-type stars are usually analyzed with static model atmospheres in local thermodynamic equilibrium (LTE) and a homogeneous plane-parallel or spherically symmetric geometry. The energy balance requires particular attention, as…
We investigate the thermal response of the atmosphere of a solar-type star to an electron beam injected from a hot Jupiter by performing a 1-dimensional magnetohydrodynamic numerical experiment with non-linear wave dissipation, radiative…