We have computed limb-darkening coefficients for five commonly used near infrared photometric bands, namely R, I, J, H, and K, using the stellar atmosphere models by Kurucz (1993). Since the behaviour of the specific intensities is very dependent on the range of effective temperatures considered, we have adopted three analytical approximations to

Estimates of the spectral linewidths of low degree (Q=0 and Q=1) 5 min p-modes obtained from Doppler shift observations in 1984, 1986, and 1987 are reported. The observed linewidths increase from 0.5 microHz at 2000 microHz to 3.8 microHz at 4300 microHz for Q = 0. Comparison with other data suggests that for a given frequency the linewidth

The iron abundance of seven stars near the main-sequence (MS) turnoff and a giant in M67 are spectroscopically derived, and the results are discussed. The resulting mean iron abundance of the turnoff stars is (Fe/H) = 0.04 + or - 0.04. Taken together with previous determinations for younger clusters, this shows that there has been relatively little

The lithium (Li) abundance measured in the solar atmosphere is 140 times smaller than expected considering the proto-solar value. Furthermore, measurements of Li abundance made for many stars similar to the Sun reveal a large dispersion. These observations have defied the models of light element depletion for decades. We present a strong evidence

GJ 569Bab is the first brown dwarf binary for which the mass of each component has been derived by solving the astrometric and spectroscopic orbit of the pair, i.e., independently of any theoretical assumption. This allows us to test the predictions of the various evolutionary models available in the literature. Particularly interesting are the

We review several experiments in ionospheric modification performed at the HAARP facility. Many of these experiments have been done in bistatic configuration with the WAVES receiver on the NASA/WIND satellite, including study of scintillation-like variations in low frequency propagation through the earth's ionosphere and magnetosphere. The