Kreidl will observe A-type (Ap) stars to search for stars with rapid oscillations (periods of a few minutes). An accurate measure of the period is possible, permitting very detailed checks on theoretical models. Kreidl will also measure stellar variability on time scales of hours, to determine the nature of sporadic variations and to relate any regular variations to other (delta Scuti) variable stars with similar colors and luminosities. Many stars pulsate, growing and shrinking regularly. The pulsations have taught us much about the interior of those stars. A new kind of stellar oscillations has now been observed, involving horizontal as well as radial motions. Observed solar oscillations already provide qualitatively new information on the solar interior. Kreidl will investigate one group of oscillating stars, performing the first search in the northern hemisphere and measuring oscillation periods more accurately than is possible on the Sun. The telescopes of the Lowell Observatory allow the extended observing times needed to measure oscillations and other forms of stellar variability.
