Related papers: NEW INSIGHTS INTO NON-RADIATIVE HEATING IN LATE-A …

We report the detection of N V 1239 A transition region emission in HST/GHRS spectra of the A7 V stars, Alpha Aql and Alpha Cep. Our observations provide the first direct evidence of 1-3 x 10^5 K material in the atmospheres of normal A-type…

Previously unrecognized weak emission lines originating from high excitation states of Si II (12.84 eV) and Al II (13.08 eV) are detected in the red region spectra of slowly rotating early B-type stars. We surveyed high resolution spectra…

FUSE ultraviolet spectra of 8 giant and supergiant stars reveal that high temperature (3 X 10^5 K) atmospheres are common in luminous cool stars and extend across the color-magnitude diagram from Alpha Car (F0 II) to the cool giant Alpha…

We use the ROSAT public data archive to study the X-ray emission of a sample of supposedly single A0-F6 spectral type stars from the Bright Star Catalogue. We detected X-ray emission from 19 A and 33 F-type stars. However, our results are…

We investigate if the super-saturation phenomenon observed at X-ray wavelengths for the corona, exists in the chromosphere for rapidly rotating late-type stars. Moderate resolution optical spectra of fast rotating EUV- and X-ray- selected…

If magnetic activity in outer stellar atmospheres is due to an interplay between rotation and subsurface convection, as is generally presumed, then one would not expect to observe indicators of activity in stars with T_eff > 8300 K. Any…

M dwarfs produce explosive flare emission in the near-UV and optical continuum, and the mechanism responsible for this phenomenon is not well-understood. We present a near-UV/optical flare spectrum from the rise phase of a secondary flare,…

Cool stars on the main sequence generate X-rays from coronal activity, powered by a convective dynamo. With increasing temperature, the convective envelope becomes smaller and X-ray emission fainter. We present Chandra/HRC-I observations of…

The precise mechanisms that provide the non-radiative energy for heating the chromosphere and the corona of the Sun and other stars are at the focus of intense contemporary research. Observations at submm/mm wavelengths are particularly…

Sulfur and its isotopic ratios play a crucial role in understanding astrophysical environments, providing insights into nucleosynthesis, ISM processes, star formation, planetary evolution, and galactic chemistry. We investigate the…

The precise mechanisms that provide the non-radiative energy for heating the chromosphere and the corona of the Sun and those of other stars constitute an active field of research. By studying stellar chromospheres one aims at identifying…

We present a new scenario for the cooling of compact stars considering the central source of Cassiopeia A (Cas A). The Cas A observation shows that the central source is a compact star that has high effective temperature, and it is…

We determine rotation periods of a sample of 48 late F-type to mid-M dwarf stars using time-series high-resolution spectroscopy of the Ca II H&K and H-alpha chromospheric activity indicators. We find good agreement between the rotation…

We present a model atom for C I - C II - C III - C IV using the most up-to-date atomic data and evaluated the non-local thermodynamic equilibrium (NLTE) line formation in classical 1D atmospheric models of O-B-type stars. Our models predict…

We analyze HST/GHRS spectra of AB Doradus, the prototypical ultra-rapidly rotating K dwarf. We observed chromospheric (Mg II) and transition region (C II, Si IV, C IV, and N V) lines periodically throughout the stellar rotation period, and…

In the disks of spiral galaxies, diffuse soft X-ray emission is known to be strongly correlated with star-forming regions. However, this emission is not simply from a thermal-equilibrium plasma and its origin remains greatly unclear. In…

High-precision interferometric observations of six early-type main sequence stars known to harbour cold debris discs have been obtained in the near-infrared K band with the FLUOR instrument at the CHARA Array. The measured squared…

We report on the detection of the [CII] 157.7 $\mu$m emission from the Lyman break galaxy (LBG) MACS0416_Y1 at z = 8.3113, by using the Atacama Large Millimeter/submillimeter Array (ALMA). The luminosity ratio of [OIII] 88 $\mu$m (from…

High-energy emission spectra from the outer atmospheres of late-type stars represent an important feature of the stellar activity in several contexts, such as the photoevaporation and photochemistry of planetary atmospheres or the modeling…

We present spectrophotometric data from 0.4 to 4.2 microns for bright, northern sky, Be stars and several other types of massive stars. Our goal is to use these data with ongoing, high angular resolution, interferometric observations to…