Showing papers by "A. C. Lanzafame published in 1998"
Journal Article•
TL;DR: In this paper, the authors compared the capabilities of LTE atmo-spheric models of including millions of lines contributing to the opacity and accurate NLTE treatment of the line formation.
Abstract: Spectra in the visible range 410 - 710 nm have been obtained for a sample of main sequence B-type stars to deter- mine the behavior of neutral helium lines with effective temper- ature and gravity. Equivalent widths have been compared with new calculations which combine the capabilities of LTE atmo- spheric models of including millions of lines contributing to the opacity and accurate NLTE treatment of the line formation. The latter take advantage of accurate atomic cross-sections. We nd a satisfactory agreement between theory and observations with differences probably due to the microturbulence. We also investigate the effects of blending and nd that the Hei412.1nm is severely blended with oxygen lines for spectral types earlier than B3.
5 citations
01 Jan 1998
TL;DR: In this article, the authors describe multi-wavelength, simultaneous observations of the RS CVn star II Pegasi, most of which were obtained during the first three weeks of September 1992.
Abstract: We describe multi-wavelength, simultaneous observations of the RS CVn star, II Pegasi, most of which were obtained during the rst three weeks of September 1992. These observations were made using optical and infra-red broad-band photometry, ultraviolet and opti- cal spectroscopy and microwave monitoring. We have de- tected photospheric spots and chromospheric flares, as well as deriving a description of mean conditions in the quiet chromosphere. One of the flares, observed in opti- cal photometry and ultraviolet spectroscopy is one of the most energetic ever observed on this star. We demonstrate that in its \quiescent" state II Peg is continually variable in most of its chromospheric emissions, as well as in its coronal output.
1 citations