The Optical Gravitational Lensing Experiment. Cepheids in the Magellanic Clouds. II. Single-Mode Second Overtone Cepheids in the Small Magellanic Cloud

摘要

We present a sample of 13 candidates for single-mode second overtone Cepheidsdiscovered in the 2.4 square degree area of the SMC bar during the OGLEmicrolensing search. All candidates passed four photometric tests: analysis ofFourier parameters of the light curve, R_21 and \phi_21, position in theperiod-luminosity diagram and location in the color-magnitude diagram. The stars form a very homogeneous group of objects with very similar lightcurves of low amplitude and almost sinusoidal shape. Their color indices B-Vand V-I are also very similar and the objects determine the observational blueedge of the instability strip of the first overtone Cepheids. This is the firstfirm sample of the single-mode second overtone Cepheids detected so far.