Related papers: Spots, plages, and flares on lambda Andromedae and…
This study explores photometric variability in a sample of hot stars in order to test whether variability arises from rotational modulation due to surface temperature spots. Frequencies determined from the projected rotational velocities…
Magnetic activity in the photosphere and chromosphere of the M dwarf EY Dra is studied and possible correlations between the two are investigated using photometric observations in the V and R bands and optical and near infrared…
We study flare processes in the lower solar atmosphere using observational data for a M1-class flare of June 12, 2014, obtained by New Solar Telescope (NST/BBSO) and Helioseismic Magnetic Imager (HMI/SDO). The main goal is to understand…
We study the connection between the chromospheric and photospheric behaviour of the active late-type star FK Comae. We use spot temperature modelling, light curve inversion based on narrow- and wide-band photometric measurements, Halpha…
Plages are small concentrations of strong, nearly vertical magnetic fields in the solar photosphere that expand with height. A high spatial and spectral resolution that can resolve their fine structure is required to characterize them, and…
We have modeled irradiated planets located near a dM5 and a G2 primary star. The impinging radiation field was explicitly included in the solution of the radiative transfer equation and in the computation of the atmospheric structure. We…
We have analysed the photometric data obtained with the STEREO spacecraft for 558 non-magnetic chemically peculiar (CP) stars to search for rotational and pulsational variability. Applying the Lomb-Scargle and the phase dispersion…
The inhomogeneous surface distribution of heavy elements is known to cause periodic light variability of magnetic chemically peculiar stars. It is unclear to what extent the same paradigm applies to mercury-manganese (HgMn) stars. We aim to…
Surges have regularly been observed mostly in H$_{\alpha}$ 6563~{\AA} and Ca~{\sc ii} 8542~{\AA}. However, surge$'$s response to other prominent lines of the interface-region (Mg~{\sc ii} k 2796.35~{\AA} $\&$ h 2803.52~{\AA}, O~{\sc iv}…
The origin of the near-ultraviolet and optical continuum radiation in flares is critical for understanding particle acceleration and impulsive heating in stellar atmospheres. Radiative-hydrodynamic simulations in 1D have shown that high…
The evolution of starspots of the giant primaries of RS CVn systems is typically detected indirectly with photometric and spectroscopic monitoring. These observations suggest slowly-evolving stellar surfaces and can constrain differential…
Cassini's Composite Infrared Spectrometer (CIRS) observed both of Rhea's polar regions during two flybys on 2013/03/09 and 2015/02/10. The results show Rhea's southern winter pole is one of the coldest places directly observed in our solar…
We propose a general principle that under the radiative-convective equilibrium, the spatial and temporal variations in a planet's surface and atmosphere tend to increase its cooling. This principle is based on Jensen's inequality and the…
Context: On 2022 May 4, an M5.7 flare erupted in the active region NOAA 13004, which was the target of a coordinated campaign between GREGOR, IRIS, Hinode, and ground-based instruments at the Ond\v{r}ejov observatory. A flare kernel located…
The UV and optical spectra from the HST FOS and from the FAST spectrograph at the Whipple Observatory at different phases are analysed, leading to new results about the configuration of AG Peg. Consistent modelling by the code SUMA, which…
Solar mid-IR observations in the 8-15 micrometer band continuum with moderate angular resolution (18 arcseconds) reveal the presence of bright structures surrounding sunspots. These plage-like features present good association with calcium…
We consider the atmospheric flow on short-period extra-solar planets through two-dimensional numerical simulations of hydrodynamics with radiation transfer. One side is always exposed to the irradiation from the host star. The other is…
We measure starspot filling fractions for 240 stars in the Pleiades and M67 open star clusters using APOGEE high-resolution H-band spectra. For this work we developed a modified spectroscopic pipeline which solves for starspot filling…
As photosynthesis on Earth produces the primary signatures of life that can be detected astronomically at the global scale, a strong focus of the search for extrasolar life will be photosynthesis, particularly photosynthesis that has…
We have used high-speed spectroscopy of the rapidly oscillating Ap (roAp) star HD99563 to study the pulsation amplitude and phase behaviour of elements in its stratified atmosphere over one 2.91-d rotation cycle. We identify spectral…