Browsing by Author "Griest, R"

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    The MACHO project sample of galactic bulge high-amplitude δ Scuti stars
    (2000) Alcock, C; Allsman, RA; Alves, DR; Axelrod, TS; Becker, AC; Bennett, DP; Cook, KH; Freeman, KC; Geha, M; Griest, R; Lehner, MJ; Marshall, SL; McNamara, BJ; Minniti, D; Nelson, C; Peterson, BA; Popowski, P; Pratt, MR; Quinn, PJ; Rodgers, AW; Sutherland, W; Templeton, MR; Vandehei, T; Welch, DL
    We have detected 90 objects with periods and light-curve structures similar to those of held delta Scuti stars using the Massive Compact Halo Object (MACHO) Project database of Galactic bulge photometry. If we assume similar extinction values for all candidates and absolute magnitudes similar to those of other field high-amplitude delta Scuti stars (HADS), the majority of these objects lie in or near the Galactic bulge. At least two of these objects are likely foreground delta Scuti stars, one of which may be an evolved nonradial pulsator, similar to other evolved, disk-population delta Scuti stars. We have analyzed the light curves of these objects and find that they are similar to the light curves of held delta Scuti stars and the delta Scuti stars found by the Optical Gravitational Lens Experiment (OGLE). However, the amplitude distribution of these sources lies between those of low- and high-amplitude delta Scuti stars, which suggests that they may be an intermediate population. We have found nine double-mode HADS with frequency ratios ranging from 0.75 to 0.79, four probable double- and multiple-mode objects, and another four Objects with marginal detections of secondary modes. The low frequencies (5-14 cycles day(-1)) and the observed period ratios of similar to 0.77 suggest that the majority of these objects are evolved stars pulsating in fundamental or first overtone radial modes.