Line blanketing

Astronomical Observatory, were used to carry out the calculations of theoretical equivalent widths of lines, synthetic spectra and a set of plane parallel, line-blanketed, flux constant LTE model atmospheres. The effective temperatures of the stars were determined from photometry, the infrared flux method and corrected, if needed, in order to achieve the LTE excitation balance in the iron abundance results. The gravities were found by forcing Fe I and Fe II to yield the same iron abundances. The microturbulent velocities were determined by forcing Fe I line abundances to be independent of the equivalent width. For more details on the method of analysis and atomic data see Tautvaisiene et al. (2001). 

A vast and very complete data set for atoms and ions, with very variable accuracy (but sufficient for statistical calculations of line blanketing for model atmospheres in which molecules are not too important), is given by... 

LTE line-blanketed models and spectrum synthesis programs for stars hotter than reff = 5500 K are under continuing development by R. L. Kurucz at the Smithsonian Astrophysical Observatory, Cambridge, Mass., and available from their author in CD-Rom or on his website http //kurucz.harvard.edu/. 

The compact initial state of the supernova ensured that the initial colour evolution is about five times faster than a normal Type IL At five to seven days the (B - V) colour evolution accelerated as line blanketing, initially from higher members of the Balmer series, but later from metal lines, mainly from the iron group, becomes important The climb towards maximum was accomplished at an almost constant temperature as measured by the (V - I) colour, but a further decline in temperature was seen in the post-maximum phase as the luminosity collapsed towards the radioactive tail. An increse in (U - B) occurred at 40 - 50 days, but this does not correspond to any change in photospheric temperature. This is presumably the result of a composition change working its way out to the photosphere. 

Much of the attraction of electricity for Lenin had to do with its perfection, its mathematical precision. Man s work and even the work of the steam-driven plow or threshing machine were imperfect the operation of an electric machine, in contrast, seemed certain, precise, and continuous. Electricity was also, it should be added, centralizing. It produced a visible network of transmission lines emanating from a central power station from which the flow of power was generated, distributed, and controlled. The nature of electricity suited Lenin s utopian, centralizing vision perfectly. A map of electric lines from the generating plant would look like the spokes of a centralized transportation hub like Paris (see chapter 1), except that the direction of flow was one way. Transmission lines blanketed the nation with power... 

In particular, the improved models include the effects of the far-UV absorption lines (line blanketing), omitted in early models, and predict lower far-UV fluxes for a given temperature. Figure 14 shows a series of model atmosphere flux distributions, computed by E. Avrett of the Harvard-Smithsonian Center for Astrophysics. As can be seen, the flux distributions of hot stars are far more sensitive to temperature in the far-UV range than in the ground-accessible wavelength range. 

FIGURE 14 Shown are model atmosphere flux distributions, more recent than those in Fig. 13, taking into account absorption line blanketing. Effective temperatures for the models are as indicated, from top to bottom. [Reprinted with permission from Kurucz, R. L. (1979). Astrophys. J. Suppl. 40, 1.]... 

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