We report the likely optical ID of the bright transient recently discovered in M31, CXOM31 J004253.1+411422 (Henze et al, ATEL #2356). With a peak X-ray luminosity of nearly 5e39 erg/sec, this is the brightest X-ray transient yet found in M31. An approximately 4000 second HST exposure on 21 Jan 2010, using the ACS and F435W filter, finds an

We present new empirical estimates of the ΔV bump HB parameter for 15 Galactic globular clusters (GGCs) using accurate and homogeneous ground-based optical data. Together with similar evaluations available in the literature, we ended up with a sample of 62 GGCs covering a very broad range in metal content (-2.16 dex

We report on a detailed radiative transfer modeling of the observed scattering polarization in the Hα line, which allows us to infer quantitative information on the magnetization of the quiet solar chromosphere. Our analysis suggests the presence of a magnetic complexity zone with a mean field strength langBrang > 30 G lying just below the sudden

We present a detailed study of the hydrodynamics of the matter reinserted by massive stars via stellar winds and supernovae explosions in young assembling galaxies. We show that the interplay between the thermalization of the kinetic energy provided by massive stars, radiative cooling of the thermalized plasma, and the gravitational pull of the

The ability of new instruments for providing accurate inferences of vector magnetic fields and line-of-sight velocities of the solar plasma depends a great deal on the sensitivity to these physical quantities of the spectral lines chosen to be measured. Recently, doubts have been raised about visible Stokes profiles to provide a clear distinction

Available from the Minor Planet Center.