We present a comparison between images of comet C/1995 O1 (Hale-Bopp) obtained from 12 March to 9 May 1997, with two telescopes of the Observatorio del Teide (IAC, Tenerife, Spain) in visible (Johnson-V filter) and three near-infrared narrowband filters (Brγ (2.166 μm), CO (2.295 μm), and Kcon (2.260 μm)). No significant differences are observed

We present the first results of our program of spectroscopic observations with orbital phase resolution of short-period active binaries. We have collected simultaneous data in the lines Hα, Hβ, and the infrared triplet (IRT) of Ca II (8498 and 8542 A). In this paper we discuss the methods used to analyze the spectra and describe the results

The three major spiral galaxies in the Local Group are known to be warped. The question is investigated of whether or not these three warps are aligned. Using available HI observations we find that they are noticeably aligned. Vectors defining the warp orientation form the following angles: [M 31, M 33]=33°; [M 31, Milky Way]=35°; [M 33, Milky Way]

Long slit spectrophotometry of the bipolar planetary nebula IC 4406, in the range from 360 to 930nm, has been used to study the chemical structure along its major axis. We find that: - the He, O, N, Ne, and Ar abundances are constant, within errors, along the major axis of the nebula. Average values for He/H, O/H, N/H, Ne/H, and Ar/H are: 0.126, 5

We describe and apply the methods that have been developed to calibrate the Advanced Stokes Polarimeter and to compensate for the polarization effects introduced by the Vacuum Tower Telescope at the National Solar Observatory/Sunspot. A seven-parameter model of the telescope is fitted to data obtained at a variety of mirror angles using

Light stops can give a strong first order electroweak phase transition in the Minimal Supersymmetric Standard Model (MSSM) satisfying one of the necessary conditions for electroweak baryogenesis. I discuss the region of parameter space where this occurs using a perturbative analysis of the Higgs effective potential. Two-loop QCD corrections