The process of $ u ar{ u}$ radiation from a relativistic plasma of electrons and positrons is studied within the Random Phase Approximation.

We present high-resolution (R ~ 60,000) optical spectra of a carefully selected sample of heavily obscured and presumably massive O-rich asymptotic giant branch (AGB) stars in the Magellanic Clouds. We report the discovery of strong Rb I lines at 7800 Å in four Rb-rich LMC stars at luminosities equal to or greater than the standard adopted

The authors report photoelectric and CCD photometry of V651 Mon, the central star of the planetary nebula NGC 2346, made in April - May and November, 1992. During each of these two epochs an occultation was measured, of amplitude 0.20 and 0.35 in the observed V magnitude, in accordance with previous results. These variations may be interpreted in

Context. Accurate star formation histories (SFHs) of galaxies are fundamental for understanding the build-up of their stellar content. However, the most accurate SFHs - those obtained from colour-magnitude diagrams (CMDs) of resolved stars reaching the oldest main-sequence turnoffs (oMSTO) - are presently limited to a few systems in the Local Group

By isolating the red clump giant population in the color-magnitude diagrams and inverting their star counts, we can obtain directly the density distribution of the old stellar population along the line of sight. We have applied this method to several near infrared surveys and obtained information on the disc, bulge and long bar. The disc is well

Context. Several clusters of red supergiants have been discovered in a small region of the Milky Way close to the base of the Scutum-Crux Arm and the tip of the Long Bar. Population synthesis models indicate that they must be very massive to harbour so many supergiants. Amongst these clusters, Stephenson 2, with a core grouping of 26 red