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Peytremann, E.

Publications and source records attributed to Peytremann, E..

8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

A table of semiempirical gf values. Part 1: Wavelengths: 5.2682 nm to 272.3380 nm

The gf values for 265,587 atomic lines selected from the line data used to calculate line-blanketed model atmospheres are tabulated. These data are especially useful for line identification and spectral synthesis in solar and stellar spectra. The gf values are calculated semiempirically by using scaled Thomas-Fermi-Dirac radial wavefunctions and eigenvectors found through least-squares fits to observed energy levels. Included in the calculation are the first five or six stages of ionization for sequences up through nickel. Published gf values are included for elements heavier than nickel. The tabulation is restricted to lines with wavelengths less than 10 micrometers.

Kurucz, R. L.↗
NASA NTRS1974

Ultraviolet television data from the orbiting astronomical observatory. II - Stellar ultraviolet colors and interstellar extinction

The results from the Celescope Catalog of Ultraviolet Stellar Observations (Davis, Deutschman, and Haramundanis 1973) are studied, emphasizing statistical groups and subgroups of stars. In spite of the rather large observational errors, the great number of Celescope observations make it possible to do that kind of study with reasonable accuracy. Some stars have ultraviolet colors that differ significantly from those of the group to which they have been assigned on the basis of ground-based observations. An attempt is made to describe the general properties of the ultraviolet colors of the stars as observed by the Celescope experiment on board NASA's Orbiting Astronomical Observatory (OAO-2). Besides the direct applicability of these results to the general study of stellar atmospheres and of interstellar extinction, they are also considered as a frame of reference for further studies of individual stars and groups of stars.

Peytremann, E.↗
NASA NTRS1972

Theoretical effect of various broadening parameters on ultraviolet line profiles.

The relative importance of various damping parameters in UV lines under conditions of normal stellar atmospheres is studied, giving attention to temperatures in the range from 10,000 to 30,000 K. It is found that the damping by electron collisions is always much smaller than either the radiative or the classical damping, except for lines that arise from high-excitation levels and do not therefore develop strong damping wings. A damping constant equal to 10 times the classical value is always much too large when compared to the more realistic (electron + radiative) damping.

Peytremann, E.↗
NASA NTRS1972

Stellar ultraviolet colors and interstellar extinction

A sample of celescope results is studied. Most of the sample stars belong to the Orion and Vela regions. Stars with visual excess E(B-V) less than 0.05 are selected in order to derive relationships of intrinsic color index versus spectral type. The resulting intrinsic color-color relations are compared with existing blanketed and unblanketed model calculations. Finally, the preceding intrinsic relations are utilized to derive some results on interstellar extinction. Owing to the rather large scatter in the celescope data, the Vela stars give the more significant results because their visible excess E(B-V) is, in general, larger than that for the Orion stars.

Peytremann, E.↗
NASA NTRS1972

Theoretical effect of various broadening parameters on ultraviolet line profiles

The relative importance of various damping parameters in ultraviolet lines under conditions of normal stellar atmospheres are studied. It is found that the damping by electron collisions is always much smaller than either the radiative or the classical damping, except for lines that arise from high excitation levels and do not therefore develop strong damping wings. A damping constant equal to 10 times the classical value is always much too large when compared to the more realistic (electron + radiative) damping.

Peytremann, E.↗