ISSN:
1573-093X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract An attempt is made to detect the lines of Mg25H and Mg26H in the photospheric spectrum, using calculated isotope shifts. From comparisons with the Mg24H lines of the 2 Σ−2 Π transition in the (0, 0) band the ratios Mg25/Mg24 = 0.12 ± 0.04 and Mg26/Mg24 = 0.12 ± 0.02 are derived. These are essentially the same as the terrestrial ratios. The profile of one line of Mgi confirms these values. The wavelengths of MgH and C2 lines, when corrected for the gravitational red shift, indicate that macroturbulent (or streaming) velocities die out near log τ0 = − 1.0. From the equivalent widths of the MgH lines a rotational temperature of 5132 ± 200 K is obtained and compared to predictions from various model atmospheres. The band oscillator strength is found to be 0.024 ± 0.002, in serious disagreement with the single laboratory determination. The profiles of MgH, C2, CN and some weak atomic lines are used to derive the variation of the radial component of microturbulence with optical depth, on the assumption of streaming velocities of 2.5–3.0 km/sec. A slow increase with increasing height in the photosphere is found, over the range −1.5 〈 logτ0〈 0.2. The center-limb variation of the equivalent widths of MgH and C2 lines for a wholly inhomogeneous model is found to be the same as for a model which is homogeneous above log τ0 = - 1.0. With such a model as the latter, the center-limb variation of the profiles of the selected molecular and atomic lines is moderately-well reproduced by an anisotropic microturbulent velocity with a tangential component of 3 km/sec which seems to be constant with height over the range considered.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00147141
Permalink
