The Cometary Knots in the Helix Nebula have shown themselves to be formed of a head which is a photoionized surface, optically thick to Lyman continuum radiation, on the central star facing sides of neutral clumps and a cometary tails photionized by the diffuse radiation field. In this study we will present the results of a photoionization model of

We present results of numerical 3D simulation of propagation of MHD waves in sunspots. We used two self consistent magnetohydrostatic background models of sunspots. There are two main differences between these models: (i) the topology of the magnetic field and (ii) dependence of the horizontal profile of the sound speed on depth. The model with

We studied the nuclear obscuration of galaxies hosting Low Ionization Narrow Emission Regions (LINERs) based on their X-ray and optical emission. X-ray data show that high obscuration is a common property of LINERs, 50% of them are identified as good candidates to be Compton-thick. From the Hα HST-imaging analysis it is found that the large

Available from the Minor Planet Center.

Context: Classical T Tauri stars are young solar-type stars accreting material from their circumstellar disks. Thanks to a favorable inclination of the system, the classical T Tauri star AA Tau exhibits periodic optical eclipses as the warped inner disk edge occults the stellar photosphere. Aims: We intend to observe the X-ray and UV emission of AA

One fundamental question about pulsars concerns the mechanism of their pulsed electromagnetic emission. Measuring the high-end region of a pulsar’s spectrum would shed light on this question. By developing a new electronic trigger, we lowered the threshold of the Major Atmospheric γ-ray Imaging Cherenkov (MAGIC) telescope to 25 giga-electron volts