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We present a qualitative physical model of the origin of two very brightUV lines of Fe II at 2507-2509 Å, present in high-resolutionspectra of gaseous condensations (blobs) close to the central star ofeta Carinae. The spectra have been obtained with the Hubble SpaceTelescope (HST). The model is based on a type of Bowen mechanism withselective photoexcitation of Fe II by a broad HLyalpha profile,ge

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We consider possible schemes for the resonance-enhanced two-photon ionization (RETPI) of Ne and Ar atoms under the action of bichromatic radiation of intense resonance lines of HI, HeI, and HeII in a radiation-rich astrophysical plasma. The ionization rate is comparable to or exceeds the recombination rate in rarified astrophysical plasma, which leads to the accumulation of singly ionized ions wit

Both the Fe II UV emission in the 2000-3000 Å region [Fe II(UV)]and resonance emission line complex of Mg II at 2800 Å areprominent features in quasar spectra. The observed Fe II(UV)/Mg IIemission ratios have been proposed as means to measure the buildup ofthe Fe abundance relative to that of the alpha-elements C, N, O, Ne,and Mg as a function of redshift. The current observed ratios show largesca

Using a numerical simulation of compressible convection with radiativetransfer mimicking the solar photosphere, we compare the velocity fieldderived from granule motions to the actual velocity field of the plasma.We thus test the idea that granules may be used to trace large-scalevelocity fields at the sun's surface. Our results show that this isindeed the case provided the scale separation is suf

P-mode oscillations in the Sun and stars are excited stochasticly by Reynolds stress and entropy fluctuations produced by convection in their outer envelopes. The excitation increases with increasing effective temperature (until envelope convection ceases in the F stars) and also increases with decreasing gravity.

We present the FERRUM Project, an international collaboration aiming at a production and evaluation of oscillator strengths (transition probabilities) of selected spectral lines of singly ionized iron group elements, that are of astrophysical relevance. The results obtained include measurements and calculations of permitted and forbidden lines of Fe II. The data have been applied to both emission

We have used the Cerro Tololo Inter-American Observatory telescopes andspectrographs to record emission lines in eta Carinae from 3093 to8956 Å with a gap between 4432 and 5696 Å. A resolving powerof about 20,000 was used throughout. Accurate wavelengths, peakintensities relative to the local continuum, and line identificationsare presented. The data are briefly discussed with respect to the state

Within the framework of a simple model of photophysical processes in the Weigelt blobs in the vicinity of the luminous blue variable (LBV) star eta Carinae, we explain the presence of the fluorescent < O I > 8446-angstrom and forbidden [O I] 6300-angstrom lines as well as the absence of the allowed O I 7774-angstrom line in spectra recorded with the Hubble Space Telescope (HST)/STIS instrument (Gu

We have derived elemental abundances of O, Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Co, Ni as well as for a number of s-elements for 47 G and K dwarf, with [Me/H]>0.1 dex. The selection of stars was based on their kinematics as well as on their uvby-beta photometry. One sample of stars on rather eccentric orbits traces the chemical evolution interior to the solar orbit and another, on circular orbits,

The dust detector system onboard Galileo has recoding dust impacts incircumjovian space since the spacecraft was injected into a bound orbitabout Jupiter in December 1995. This is the sixth in a series of papersdedicated to presenting Galileo and Ulysses dust data. We present datafrom the Galileo dust instrument for the period January to December 1996when the spacecraft completed four orbits about

A brief description of the operational principles of an Electron Beam Ion Trap is given with specific reference to the currently under development/construction Shanghai EBIT. This is followed by an introduction to some of the frontier physics problems of highly charged ions that can be studied with such devices. Also a discussion of the use of EBITs as a powerful tool in hot-plasma diagnostics is

Two short (< 2 s) gamma-ray bursts (GRBs) have recently been localized(1-4) and fading afterglow counterparts detected(2-4). The combination of these two results left unclear the nature of the host galaxies of the bursts, because one was a star-forming dwarf, while the other was probably an elliptical galaxy. Here we report the X-ray localization of a short burst (GRB 050724) with unusual gamma-ra

We report on a new survey of metallicities, ages, and Galactic orbitsfor a complete, magnitude-limited, and kinematically unbiased all-skysample of 16682 nearby F- and G-dwarfs. Our~63000 new, accurate radialvelocities for nearly 13500 of the stars, combined with Hipparcosparallaxes and Tycho-2 proper motions, complete the kinematic data for14139 stars and allow us to identify most of the binary s

Measurements of dust coupled to the Jovian magnetosphere have been obtained with the dust detector on board the Galileo spacecraft. We report on data obtained during the first four orbits about Jupiter that had flybys of the Galilean satellites: Ganymede (orbits 1 and 2), Callisto (orbit 3), and Europa (orbit 4). The most prominent features observed are highly time variable dust streams recorded t