We compute photoionization models for the giant extragalactic H II region NGC 5461, and compare their predictions to several observational constraints. The models are constrained to reproduce the observed density profile, and our analysis takes into consideration the bias introduced by the shapes and sizes of the slits used by different observers.

We undertook two time-series photometric multisite campaigns for the rapidly oscillating Ap star HD 122970. The first one, conducted in 1998, resulted in 119h of data and in the detection of three pulsation frequencies. The presence of possible further modes which held the promise of deriving a mode identification motivated a second worldwide

Several authors have suggested that a link exists between the flux of galactic cosmic rays (GCR) and cloudiness. Here we review the evidence for such a connection from studies of cloud factors using both satellite and ground-based data. In particular, we search for evidence for the low cloud decrease predicted by the rising levels of solar activity

We demonstrate that the atomic alignment of the hyperfine-structure components of the ground-level S1/2 of Na I and of the upper-level P1/2 of the D1 line are practically negligible for magnetic strengths B>10 G and virtually zero for B>~100 G. This occurs independently of the magnetic field inclination on the stellar surface (also, in particular

During the post-AGB phase the dust shell detaches from the central star and dust temperatures varies between 100 and 200 K. In order to study the onset of photo-ionization in post-AGB stars, IRSPEC near-infrared spectroscopy of 40 IRAS sources from the Point Source Catalogue was conducted. In 27 of the post-AGB observed Br gamma is detected. In

We discuss here the nature of a rich zoo of knots, filaments, jets and jet-like systems, located--in terms of morphology and kinematics--either inside or outside the main nebular bodies of planetary nebulae (PNe). These features are low-ionization structures (LISs) especially prominent in [N II] and other low-ionization line emission, which are