Ultra high energy photons and neutrinos are carriers of very important astrophysical information. They may be produced at the sites of cosmic ray acceleration or during the propagation of the cosmic rays in the intergalactic medium. In contrast to charged cosmic rays, photon and neutrino arrival directions point to the production site because they

Ultraviolet IUE spectra and infrared JHKL photometry of FG Sge obtained over the period 1982-1989 indicate that the cooling rate of the star observed until about 1980 seems to have stopped and that an increase of the effective temperature may have occurred, this being a significant change in the evolutionary path traced so far. The current spectral

The mid-infrared range contains many spectral features associated with large molecules and dust grains such as polycyclic aromatic hydrocarbons and silicates. These are usually very strong compared to fine-structure gas lines, and thus valuable in studying the spectral properties of faint distant galaxies. In this paper, we evaluate the capability

Aims: We analyze a set of full Stokes profile observations of the flaring active region NOAA 10808. The region was recorded with the Vector-Spectromagnetograph of the Synoptic Optical Long-term Investigations of the Sun facility. The active region produced several successive X-class flares between 19:00 UT and 24:00 UT on September 13, 2005 and we

The peculiar low-mass X-ray binary XSS J12270-4859, associated with the Fermi/LAT source 2FGL J1227.7-4853, was in an X-ray, gamma-ray and optical low-luminosity persistent state for about a decade until the end of 2012, when it entered into the dimmest state ever observed. The nature of the compact object has been controversial until the detection

Aims: The fine-structure of the magnetic field in a sunspot penumbra in the upper chromosphere is to be explored and compared to that in the photosphere. Methods: Spectropolarimetric observations with high spatial resolution were recorded with the 1.5-m GREGOR telescope using the GREGOR Infrared Spectrograph (GRIS). The observed spectral domain