The question of efficiency of radiative energy losses in spectral lines is addressed. In a semi-infinite atmosphere with constant temperature, the total radiative energy loss (integrated over all depths) in a spectral line without continuum is infinite, in both LTE and non-LTE. Thus, only local energy balances may be considered with such models

High-resolution spectra of Alpha Cen B, Xi Boo A, 70 Oph A, and Epsilon Ind obtained using the Coude Echelle Spectrometer and the 1.4-m Coude Auxiliary Telescope of ESO are analyzed. Variations in the normalized fluxes for the four dwarfs are described. Position and intensity measurements of the Ca II H features are examined. The use of the spectra

This paper presents an automatic method for (1) digital estimation of the width of the atmospherical seeing in astronomical images of extended objects and (2) image restoration by using the constrained Jansson-Van Cittert deconvolution algorithm. The estimation of the seeing is achieved by computing the radial profile of the averaged log spectrum

Synthetic horizontal branches, constructed on the basis of Sweigart and Gross (1976) horizontal branch star models and of the recently revised theoretical instability strip (Stellingwerf, 1984) are presented for various chemical compositions appropriate for Population II systems, for various assumptions on the mass size of the helium core and for

Periodic orbits of the bicircular problem and their stability; numerical simulations of the motion in an extended neighborhood of the triangular libration points in the Earth-Moon system; the equations of motion; periodic orbits of intermediate equations; a semianalytical approach to the quasi-periodic solution of the global equations; numerical

Spectra of early-type stars in several heavily reddened OB associations are used to study broad diffuse bands in the range from 5700 to 6300 angstroms. The features at 5778 angstroms and 6170 angstroms correlated well with narrower lines in their vicinity. The 5795-angstrom band is not correlated with the overlapping line at 5797 angstroms but