Physics
Scientific paper
Oct 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001phdt..........h&link_type=abstract
Thesis (PhD). UNIVERSITY OF TORONTO (CANADA), Source DAI-B 62/04, p. 1902, Oct 2001, 169 pages.
Physics
Scientific paper
In this thesis, a new technique for studying convection is developed using relative line-shifts. The technique is tested using the sun's visible flux spectrum and the most current Fe I line positions available, and can be applied at significantly lower spectral resolutions and signal- to-noise ratios than has been done previously. These line-shifts show a clear dependence on both line strength and wavelength. Similar observations in the solar intensity spectrum demonstrate that the effects of limb darkening on the line-shifts are relatively minor. Because the solar intensity spectrum has been observed well into the infrared, it has been used to study the line-shift techniques over the broadest possible spectral region. The Fe I line-core shift distributions show clear evidence of a dependence on line strength at all wavelengths, and sensitivities to wavelength are found at shorter wavelengths. Line-shifts for 1323 CO lines between 2.2 and 5.5 μm are also determined. Clear evidence of a dependence on line strength is found at all wavelengths, and interesting line-shift behavior is found when the excitation energy and quantum numbers of the CO transitions are examined. A similar study of CO and OH line-shifts is done using a sunspot umbral spectrum, and the convective motions are found to be greatly suppressed. Line-shifts are also examined in the infrared spectrum of six cool giant stars. The vigorous nature of convection seems to decline with Teff, which is consistent with expectations.
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