Photometric study of the galactic open cluster M11

Abstract

The open cluster M11 (NGC 6705, Mel 213, Cr 391, OCl 76) is a concentrated, populous stellar system projected on the rich background of the Scutum star-forming field, towards the central part of the Galactic disk. Sometimes mistaken for a loose globular cluster, M11 is one of the richest and most compact of the known open clusters in the Milky Way. At the same time, the cluster is young, resembling the young globular clusters in the Magellanic Clouds. The cluster is situated in a clear area characterized by a relatively low interstellar extinction. It is important for its contribution to the understanding of evolution of massive and intermediate mass stars. In this study, the M11 cluster is investigated using Stromgren-Crawford uvby-beta photometry. This is the first uvby-beta photometry obtained for this cluster. This work involves analysis of photometric data obtained with the 0.9-m WIYN telescope at Kitt Peak National Observatory (KPNO) during two observing runs in 2007 and 2008. The primary goal of this work is to convert the raw observations to a standard photometric system. A software package called IRAF has been utilized for the reduction of this data. In the process, various techniques of stellar photometry are applied and discussed. The reduced photometry is used to classify the observed stars into spectral types, and to provide new estimates of the distance to the cluster and the extinction of stellar light.