The linear oscillations of a stratified atmosphere embedded in a uniform vertical magnetic field are studied here. We use a simple theoretical model, formed by the superposition of two isothermal layers, representing, respectively, i) the photosphere and the chromosphere, and ii) the corona. The bottom layer behaves, for some modes, as a resonant

We investigate the luminous X-ray sources in the Lockman Hole (LH) and the extended Groth strip (EGS) detected at 24{mu}m using the Multiband Imaging Photometer (MIPS) and also with the Infrared Array Camera (IRAC) on board the Spitzer Space Telescope. We assemble optical/infrared spectral energy distributions (SEDs) for 45 X-ray/24{mu}m sources in

The importance of the breakup channel in the vicinity of the Coulomb barrier (1

H1517+656 is an unusual source, even for a BL Lac object. It is one of the most luminous BL Lac objects known, with extreme emission properties at radio, optical, and X-ray frequencies. Furthermore, in our WFPC2 snapshot survey we discovered a series of peculiar arcs describing a 2.4" radius ring surrounding the source. This paper describes follow

We present accurate relative ages for a sample of 55 Galactic globular clusters. The ages have been obtained by measuring the difference between the horizontal branch and the turnoff in two internally photometrically homogeneous databases. The mutual consistency of the two data sets has been assessed by comparing the ages of 16 globular clusters in

We explore the formation and evolution of hydrogen-deficient post-AGB white dwarf stars by computing the complete evolution of an initially 2.7 Msun star from the ZAMS through the thermally pulsing and mass-loss phases, the born-again stage to the white dwarf stage. A time-dependent scheme for the simultaneous treatment of abundance changes caused