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Paper: Photometric Variability of Helium Stars in the Z-bump Instability Strip
Volume: 203, The Impact of Large-Scale Surveys on Pulsating Star Research, IAU Colloquium 176
Page: 438
Authors: Aznar Cuadrado, R.; Montañés Rodríguez, P.; Jeffery, C. S.; Pollacco, D.
Abstract: Z-bump opacities are known to excite radial pulsations in helium stars with 102~<= L/M~<=104 and Teff ~ 25 000 K. Well-studied cases are V652 Her and BX Cir. The absence of variations in the metal-poor star HD 144941 demonstrates the importance of Z-bump opacitiesto drive these pulsations. Several other helium-rich stars lie close to the theoretical blue-edge of the Z-bump instability strip. One of these, LS IV+6o2, is a known radial velocity variable. We report on recent (1999 June) observations of two helium stars close to the Z-bump instability boundary. Both appear to be variable.
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