  While it is known that the sharp-line star Vega (vsini ~ 20km/s) is actually
a rapid rotator seen nearly pole-on with low i (< 10 deg), no consensus has yet
been accomplished regarding its intrinsic rotational velocity (v_e), for which
rather different values have been reported so far. Methodologically, detailed
analysis of spectral line profiles is useful for this purpose, since they
reflect more or less the v_e-dependent gravitational darkening effect. However,
direct comparison of observed and theoretically simulated line profiles is not
necessarily effective in practice, where the solution is sensitively affected
by various conditions and the scope for combining many lines is lacking. In
this study, determination of Vega's v_e was attempted based on an alternative
approach making use of the first zero (q_1) of the Fourier transform of each
line profile, which depends upon K (temperature sensitivity parameter differing
from line to line) and v_e. It turned out that v_e and vsini could be
separately established by comparing the observed q_1^obs and calculated q_1^cal
values for a number of lines of different K. Actually, independent analysis
applied to two line sets (49 Fe I lines and 41 Fe II lines) yielded results
reasonably consistent with each other. The final parameters of Vega's rotation
were concluded as vsini = 21.6 (+/- 0.3) km/s, v_e = 195 (+/- 15) km/s, and i =
6.4 (+/- 0.5) deg.
