Following earlier work by Shields and Searle and by Mathis, the authors define a radiation softness parameter η = (O+/O++)(S++/S+), which they recommend as a criterion of effective temperature of the ionizing star(s) of H II regions that is relatively insensitive to chemical composition and ionization conditions found in optically observed nebulae

The age dependence of the recently described asymmetry of penumbrae of large stable sunspots was analyzed. Young sunspots showed shorter eastern penumbrae, which differed by a maximum of + or - 10 percent from their mean width. For older sunspots the western penumbrae became smaller than the mean penumbra, reaching differences of 20 percent for

NIR (JHK) photometry of six quasars with redshifts ranging from 3 to 3.78 is reported. None of these objects has previously been observed in the IR. Their NIR colors are bluer than those of low-redshift quasars. They do, however, exhibit a considerable scatter, which can be qualitatively explained by line-emission contamination within the IR

Near-infrared maps in the J, H, and K bands, have been obtained for the nearby flocculent spiral NGC 2403, with a linear resolution of 900 pc. Radially and azimuthally averaged profiles, and profiles in colour index are presented. The maps and the annular profiles show the presence of near-infrared spiral arms, whose contrast with the disc is

New measurements of the lithium abundance in a sample of 37 field dwarfs of low metallicity (-0.6 ≥ [Fe/H] ≥ 3.2) are presented. Combining these observations with those in the literature it is shown that extremely metal-deficient ("EMD") dwarfs ([Fe/H] ≤ -1.4) form a much more homogeneous population with regard to 7Li abundance than stars somewhat

Following the work started in 1984 to detect the solar intensity oscillations from ground (Jimenez et al., 1986), simultaneous velocity and intensity observations of 16 contiguous days of very high atmospheric quality obtained at Izana (Tenerife) have been analyzed. The frequencies of the p-mode intensity spectrum at three channels (500, 680 and