We present Rosat X-ray observations (with PSPC and HRI instruments) of a sample of radio galaxies belonging to the B2 catalog (3C31, 0206+35, 1113+29 and 1553+24). The source 3C31 (B2 0104+32) belongs to the group Arp 331 which shows emission from a diffuse hot intra-group gas and from the brightest members of the group. We discuss both the morphological and spectral features of this extended r...

Abstract We present our analysis of the Suzaku data SS Cygni (SS Cyg) from 2005 both in quiescence and outburst. A fluorescent iron Kα line bears significant information about geometry an X-ray-emitting hot plasma a cold reflector, such as surfaces white dwarf (WD) accretion disk (AD). Our reflection simulation has revealed that is located either very close to WD surface boundary layer (BL), wi...

X-ray emission from stars in the cool half of the Hertzsprung-Russell diagram is generally attributed to the presence of a magnetic corona that contains plasma at temperatures exceeding 1 million K. Coronae are ubiquitous among these stars, yet many fundamental mechanisms operating in their magnetic fields still elude an interpretation through a detailed physical description. Stellar X-ray astr...

We show that coronal magnetic dissipation in thin active sheets that sandwich standard thin accretion disks in active galactic nuclei may account for canonical electron temperatures of a few ×10K if protons acquire most of the dissipated energy. Coulomb collisions transfer energy from the ions to the electrons, which subsequently cool rapidly by inverse-Compton scattering. In equilibrium, the p...

By extrapolating from observationally derived surface magnetograms of low-mass stars we construct models of their coronal magnetic fields and compare the 3D field geometry with axial multipoles. AB Dor, which has a radiative core, has a very complex field, whereas V374 Peg, which is completely convective, has a simple dipolar field. We calculate global X-ray emission measures assuming that the ...

Neutral fluorine (F i) lines are identified in the optical spectra of several RCoronae Borealis stars (RCBs) at maximum light. These lines provide the first measurement of the fluorine abundance in these stars. Fluorine is enriched in some RCBs by factors of 800 to 8000 relative to its likely initial abundance. The overabundances of fluorine are evidence for the synthesis of fluorine. These res...

Abstract The empirical relationship between the nonthermal 5 GHz radio luminosity and soft X-ray of active stellar coronae, canonically called Güdel–Benz relationship, has been a cornerstone astronomy, as it explicitly ties emission to coronal heating mechanisms. extends from microflares on Sun coronae most stars suggesting that are heated by flare-like process. is thought originate consistent ...