High-amplitude Scuti stars are short-period pulsators, oscillating in one or two radial modes with amplitudes of a few tenths of a magnitude, with possible non-radial low-amplitude variations superimposed. They are found in the classical Cepheid instability strip on or just above the Main Sequence, in the same region as the low-amplitude multiperiodic Scuti stars. There are, however, certain characteristics that separate them from the low-amplitude pulsators: the amplitude of the light variations, and the fact that they are found in a very narrow strip in the HR-diagram (only 200-300 K wide), inside the Scuti instability strip (McNamara 1997).
Several Scuti stars have changing pulsation periods. Such changes are expected from stellar evolution, but many stars show period changes which currently cannot be described by stellar evolution theories, see Breger & Pamyatnykh (1998). These authors have collected data on period changes from a number of Scuti stars, and find that the observed change-rates are larger than what is expected from theory. The changes are furthermore equally distributed between increasing and decreasing periods, while mainly increasing periods are expected.
V 1162 Ori is a high-amplitude Scuti star discovered by Lampens (1985). It was later observed by Poretti et al. (1990), who found the star to be monoperiodic. They determined a period of 0.07868614 days and a V-amplitude of 022. Hintz et al. (1998) observed the star several years later, and found a much smaller amplitude (010), and a different period: 0.07869165 days, implying an increase of 0.5 seconds over 8.5 years. They also saw evidence of a possible second period, but were not able to determine it from their dataset. In this paper we present the results of new CCD time-series photometry of V 1162 Ori. We address the question of period- and amplitude changes in this star, and we search for a possible second period. We present new times of maximum and minimum light, and compare with previously obtained results. We show that the light of V 1162 Ori undergoes period- and amplitude changes on a short time scale.
© European Southern Observatory (ESO) 2000
Online publication: February 9, 2000