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Line Temperatures (line + temperature)

Distribution by Scientific Domains

Physics and Astronomy	80%

Selected Abstracts

A comparison of DA white dwarf temperatures and gravities from Lyman and Balmer line studies

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2001
M.A. Barstow
We present measurements of the effective temperatures and surface gravities for a sample of hot DA white dwarfs, using the Lyman line data available from the HUT, ORFEUS and FUSE FUV space missions. Comparing the results with those from the standard Balmer line technique, we find that there is a general good overall agreement between the two methods. However, significant differences are found for a number of stars, but not always of a consistent nature in that sometimes the Balmer temperature exceeds that derived from the Lyman lines and in other instances it is lower. We conclude that, with the latest model atmosphere calculations, these discrepancies probably do not arise from an inadequate theoretical treatment of the Lyman lines but rather from systematic effects in the observation and data reduction processes, which dominate the statistical errors in these spectra. If these systematic data reduction effects can be adequately controlled, the Lyman line temperature and gravity measurements are consistent with those obtained from the Balmer lines when allowance is made for reasonable observational uncertainties. [source]

Effect of non-isothermal oriented crystallization on the velocity and elongational viscosity profiles during the melt spinning of high density polyethylene fibers

POLYMER ENGINEERING & SCIENCE, Issue 7 2001
A. Makradi
Based on the experimental data of spine line temperature and percent crystallization, a time-integral constitutive equation has been used together with the degree of phase transformation theory to predict the velocity and elongational viscosity profiles. For the velocity profile, our predicted results are compared to experimental data and good agreement is found. Under a drawing force, the elongational viscosity profile shows a stress softening due to the molecular alignment; then the fiber hardens close to the take-up point, owing to filament crystallization. [source]

A comprehensive study of reported high-metallicity giant H ii regions , I. Detailed abundance analysis

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2002
Marcelo Castellanos
We present long-slit observations in the optical and near-infrared of 14 H ii regions in the spiral galaxies NGC 628, 925, 1232 and 1637, all of them reported to have solar or oversolar abundances according to empirical calibrations. For seven of the observed regions, ion-weighted temperatures from optical forbidden auroral to nebular line ratios are obtained and, for six of them, the oxygen abundances derived by standard methods turn out to be significantly lower than solar. The other one, named CDT1 in NGC 1232, shows an oxygen abundance of , and constitutes, to the best of our knowledge, the first high-metallicity H ii region for which accurate line temperatures, and hence elemental abundances, have been derived. For the rest of the regions no line temperature measurements could be made, and the metallicity has been determined by means of both detailed photoionization modelling and the sulphur abundance parameter S23. Only one of these regions shows values of O23 and S23 implying a solar or oversolar metallicity. According to our analysis, only two of the observed regions can therefore be considered as of high metallicity. These two fit the trends previously found in other high-metallicity H ii regions, i.e., N/O and S/O abundance ratios seem to be higher and lower than solar respectively. [source]

Low-frequency line temperatures of the CMB (Cosmic Microwave Background)

ANNALEN DER PHYSIK, Issue 9 2009
R. Hofmann
Abstract Based on SU(2) Yang-Mills thermodynamics we interprete Aracde2's and the results of earlier radio-surveys on low-frequency cosmic microwave background (CMB) line temperatures as a phase-boundary effect. We explain the excess at low frequencies by evanescent, nonthermal photon fields of the CMB whose intensity is nulled by that of Planck distributed calibrator photons. The CMB baseline temperature thus is identified with the critical temperature of the deconfining-preconfining transition. [source]