The Identification of Pulsation Modes of High-Amplitude δ Scuti Stars in ω Centauri and the Carina Galaxy

摘要

We analyze photometric observations of high-amplitude δ Scuti stars (HADS) in the globular cluster ω Cen and the Carina galaxy. The pulsation modes of the HADS are inferred primarily from their positions in V, log P diagrams. For ω Cen we identify nine fundamental pulsators (F), 22 first-overtone (1, O), one second-overtone (2, O), and probably two third-overtone (3, O) stars. The majority of the F pulsators have light amplitudes ΔV ≥ 0.15 mag, but two have ΔV < 0.15 mag. Four of the 1, O pulsators have ΔV > 0.15 mag, but the majority have smaller amplitudes. We find that the F pulsators tend to have more asymmetric light curves. The Carina variables are all large-amplitude variables. Fourteen are F pulsators and six are 1, O pulsators. At least one and possibly two 1,O stars appear to have asymmetric light curves unlike those found in ω Cen. The data are very uncertain, so the asymmetry may be an artifact of observational uncertainty. The HADS data along with their P-L relation are utilized to find the distances to ω Cen and the Carina galaxy and absolute magnitudes of their horizontal branches (HB) or RR Lyrae stars. We find the distances to be d = 6370 pc to ω Cen and d = 124,000 pc to the Carina galaxy. The M_υ(RR)-values for the ω Cen RR Lyrae stars are M_υ(RR) = 0.14 (Oost II variables) and M_υ(RR) = 0.28 (Oost I stars); M_υ(HB) = 0.29 for the Carina galaxy.