NGC 6811: An Intermediateage Cluster in the Kepler Field
Abstract
NGC 6811 is one of the four open clusters located in the Kepler spacecraft field of view. We obtained UBVRI photometry of the cluster on six nights (four of them photometric) with the 1.08 m Hall and 1.83 m Perkins telescopes at Lowell Observatory. The mean photometric precision ranges from better than 0.01 mag in the V, B  V, V  R, and V  I indices among stars brighter than magnitude 15 to about 0.05 mag for U  B at magnitude 18. We followed a Bayesian statistical approach using the Markov Chain Monte Carlo algorithm to determine the cluster reddening, distance, age, and iron content from a maximumlikelihood fit to stellar isochrones. Using the YaleYonsei isochrones, we derived E(B  V) = 0.066 ± 0.025, (m  M)_{ V } = 10.13 ± 0.19, age = 1.06 ± 0.19 Gyr, and Z = 0.012 ± 0.004 ([Fe/H] = 0.18) with the Padova isochrones, we found E(B  V) = 0.081 ± 0.015, (m  M)_{ V } = 10.31 ± 0.11, age = 0.94 ± 0.08 Gyr, and Z = 0.012 ± 0.002 ([Fe/H] = 0.20). The uncertainties include possible errors in the photometric zero points of ±0.01 mag, but do not include uncertainties in the models. Taking into account the differences between the two sets of models, we find the best estimate for the cluster parameters to be E(B  V) = 0.074 ± 0.024, (m  M)_{ V } = 10.22 ± 0.18, age = 1.00 ± 0.17 Gyr, and Z = 0.012 ± 0.004 ([Fe/H] = 0.19).
 Publication:

The Astronomical Journal
 Pub Date:
 January 2013
 DOI:
 10.1088/00046256/145/1/7
 Bibcode:
 2013AJ....145....7J
 Keywords:

 HertzsprungRussell and CM diagrams;
 methods: data analysis;
 open clusters and associations: individual: NGC 6811