The rich p-mode spectrum of the rapidly oscillating peculiar A star HD 60435

Eleven cool Ap stars are presently known to oscillate photometrically at low amplitudes and with periods of only several minutes. It is thought that these stars are pulsating in very high overtone p-modes of low degree and m = 0. New observations of the rapidly oscillating Ap star HD 60435 are presented. Analysis of these data shows that HD 60435 can oscillate in a number of frequencies, extending across at least 0.8 mHz, which can be identified with a series of high-overtone (13 ≤ n ≤ 28) p-modes, predominantly of degree 1 and 2. Oscillations near 1.4 mHz, detected in an earlier observing campaign, continue to dominate the frequency spectrum. They exhibit a modulation cycle, also noted in earlier observations, which agrees with the refined rotation period (7.6662 days) of the star. Most of the other oscillations are relatively transient in nature, although some are observed to recur after an absence of several nights.