M. Jerzykiewicz, G. Kopacki, A. Pigulski, Z. Kołaczkowski, S. -L. Kim
We present results of a CCD variability search in the field of the young open
cluster NGC 6834. We discover 15 stars to be variable in light. The brightest,
a multiperiodic Gamma Doradus-type variable is a foreground star. The eight
fainter ones, including a Gamma Cassiopeiae-type variable, two Lambda
Eridani-type variables, an ellipsoidal variable, an EB-type eclipsing binary,
and three variable stars we could not classify, all have E(B-V) within proper
range, thus fulfilling the necessary condition to be members. One of the three
unclassified variables may be a non-member on account of its large angular
distance from the center of the cluster. Four of the six faintest variable
stars, which include two eclipsing binaries and two very red stars showing
year-to-year variations, are certain non-members. One of the remaining two
faintest variable stars, an EA-type eclipsing binary may be a member, while the
faintest one, a W Ursae Majoris-type variable, is probably a non-member. For
6937 stars we provide the V magnitudes and (V-I)_C color indices on the
standard system. Because of nonuniform reddening over the cluster's face, a
direct comparison of these data with theoretical isochrones is not possible. We
therefore obtain E(B-V) from available UBV photometry, determine the lower and
upper bound of E(B-V) for NGC 6834, and then fit properly reddened Padova
isochrones to the data. Assuming HDE 332843, an early-F supergiant, to be a
member we get log (age/yr) = 7.70, V_0 - M_V = 12.10 mag. For 103 brightest
stars in our field we obtained the alpha index, a measure of the equivalent
widths of the Halpha line. We find Halpha emission in five stars, including the
Gamma Cas-type variable and the two Lambda Eri-type variables.
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http://arxiv.org/abs/1110.4064
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