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Abstract

High or moderately-high dispersion spectra covering the
wavelength interval 3800A° to 5000A° were obtained for ten luminous
early F-type stars and an F8Ia supergiant south of declination -15° .
These spectroscopic plates have been used to measure line blocking, the
profiles of the strongest lines (hydrogen and calcium K), and to
determine the equivalent widths of as many metal lines as possible in
this wavelength range.
The line blocking measurements, hydrogen-line profiles and
scanner or ubvy photometry data have been used with model atmosphere
predictions to determine effective temperatures and gravities. A
discrepancy between the gravity indicated by the Balmer jump and the Hy
line profiles has been found in the most luminous stars. The
gravities determined from the H profiles have been compared with
the gravities derived from cluster members and there is found to be a
small discrepancy, the gravities from the profiles being lower.
Some evidence for the presence of macroscopic turbulent motions in
the more luminous early F Ia stars and A Ia stars is presented, and it
is shown that the inclusion of a turbulent pressure term in the
equation of hydrostatic equilibrium largely removes the discrepancy
between the gravity indicated by the Hy profiles and that indicated
by the cluster members.
A study of the rotational velocities of the program stars show
that the early F Jab and lb stars exhibit very little or no
macroturbulence. The observed rotational velocity of 0 Sco (a lb
supergiant) shows that this star must have lost very little of its
angular momentum during its evolution off the main sequence and must
have rotated as a rigid body for some, if not all, of this phase of its
evolution.

Item Type:	Thesis - PhD
Authors/Creators:	Castley, John Charles
Keywords:	Supergiant stars
Copyright Holders:	The Author
Copyright Information:	Copyright 1974 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).
Additional Information:	Thesis (Ph.D.)--University of Tasmania, [1974?]. Bibliography: l. 166-171
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