The recent result obtained by Givens and Kostinski [J. Mod. Opt. 40, 471 (1993)] successfully solves the old and important problem in polarization optics of characterizing a given 4×4 matrix as a Mueller matrix from a mathematical point of view. For practical purposes, however, a further elaboration on this result is needed, namely, the problem of

Deep V and I CCD images of the loosely populated Galactic globular cluster Pal 1 and the surrounding field have been obtained with the Isaac Newton Telescope. A color-magnitude diagram (CMD) down to V(lim) 24 and a luminosity function down to V(lim) = 23.25 have been constructed. Adopting a reddening E(V - I) = 0.20 +/- 0.04 and comparing the CMD

A quantitative comparison between the Milne-Eddington (ME) inversion technique implemented by Skumanich & Lites and the SIR (Stokes Inversion based on Response Functions) proposed by Ruiz Cobo & del Toro Iniesta is presented. Numerical experiments are carried out to explore the capabilities and limitations of both diagnostic techniques. Such

Rotation curves and velocity dispersion profiles are presented for both the stellar and gaseous components along five different position angles (PA =5°, 50°, 95°, 125°, and 155°) of the nearby barred spiral NGC 6221. The observed kinematics extends out to about 80'' from the nucleus. Narrow and broad-band imaging is also presented. The radial

We have completely mapped the Galactic globular cluster NGC 1851 with large-field, ground-based VI CCD photometry and pre-repair HST/WFPC1 data for the central region. The photometric data set has allowed a V vs. (V-I) colour-magnitude diagram for ~20500 stars to be constructed. From the apparent luminosity of the horizontal branch (HB) we derive a

Following the announcement of a new period of activity of the soft gamma-ray repeater SGR 1806-20 in 1996 November, we have performed follow-up observations of the IR counterpart, which has been proposed as a luminous blue variable or B[e] star. We have found that no variability larger than 0.1 mag in the K-band is present in the data. No variation