SX Phoenicis Stars in the Globular Cluster NGC 5466

Through time-series CCD photometry of the globular cluster NGC 5466, we havedetected nine SX Phoenicis stars including three new ones. All the SX Phoenicisstars are located in the blue straggler region in the color-magnitude diagramof NGC 5466. Five of them show clearly double-radial mode features, the periodsof which are well consistent with the theoretical ratio of the first overtonemode to the fundamental mode (P$_{1H}$/P$_F$). Normally, it has not been easyto secure a P-L relation of the SX Phoenicis stars, because determination ofthe pulsational mode of the SX Phoenicis stars has been difficult. Theexistence of five SX Phoenicis stars in NGC5466 with double-radial modes allowsus to derive reliably a P-L relation for the fundamental mode of the SXPhoenicis stars. Using seven SX Phoenicis stars including five stars withdouble-radial modes, we derive a P-L relation for the fundamental mode in NGC5466, $ = - 3.25 (\pm 0.46) Log P + 14.70 (\pm 0.06), (\sigma = \pm0.04) $,corresponding to $ = - 3.25 (\pm0.46)Log P - 1.30 (\pm0.06) $ for anadopted distance modulus of $(m-M)_0=16.00$ and zero reddening.Comment: 20 figures, scheduled for the July 2004 issue of The Astronomical Journa