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ABSTRACT: We performed a time-series B, V band CCD photometric observations of the open cluster NGC 6811 to search for variable stars. A total number of 16 variables were detected including nine new ones. They are classified as 12 δ Scuti stars and four unknown type variables. The 12 δ Scuti variables are all very likely members of the cluster. This makes NGC 6811 a very important target for asteroseismology of dwarf Cepheids. In addition, we have carried out an isochrone fitting on the V vs. B–V CMD of the cluster based on theoretical models. It gives an age of log(t)=8.76±0.09 for the cluster with the solar metallicity (Z = 0.019). The distance modulus and color excess of NGC 6811 are determined to be (m-M)V=10.59±0.09 and E(B-V)=0.12±0.05, respectively. A preliminary Fourier analysis shows a few very interesting sequences of period-luminosity relations, with the fundamental mode matches the P–L relation defined by previous studies for δ Scuti variables with high precision observations. This also confirms that all the 12 δ Scuti stars observed in this work are highly probable members of NGC 6811.
New Astronomy. 14(6):584-589.
