Abstract
73 Draconis is an A2p star with a 20-day periodic variation in the strength of many metallic lines; these spectral variations have been studied by Morgan (1933), Durham (1943), and Faraggiana and Hack (1962). Rapid variations (during a few minutes) in the hydrogen lines of 73 Draconis have been observed photometrically by Wood (1964). This paper reports on three rapid nonperiodic changes that have been observed in the star's spectrum. Thirty spectrograms at 130 Â/mm were taken with the UV spectrograph attached to the 36-inch Cassegrain reflector of the Warner and Swasey Observatory. These were obtained in sets of from two to seven successive exposures to search for rapid changes on nine nights well distributed in phase over three cycles of the 20-day period. The exposure times averaged only four minutes, and this probably accounts for the fact that such variations have gone undetected in other investigations; for at higher dispersions the exposures are long enough to mask the type of changes reported here.
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