Formation, evolution, and survival of massive star clusters Proceedings IAU Symposium No. 316, 2015 C. Charbonnel & A. Nota, eds. c  International Astronomical Union 2017 doi:10.1017/S1743921316007055 Str¨omgren-Hβ photometry of the young open cluster NGC 6913 Nadia Kaltcheva 1 , Valeri Golev 2 , John Beaver 3 , Steven Lund 1 and Michael Briley 4 1 Department of Physics and Astronomy, University of Wisconsin Oshkosh, 800 Algoma Blvd., Oshkosh, WI 54901, USA email: kaltchev@uwosh.edu 2 Department of Astronomy, Faculty of Physics, St Kliment Ohridski University of Sofia, 5 James Bourchier Blvd., BG-1164 Sofia, Bulgaria email: valgol@phys.uni-sofia.bg 3 University of Wisconsin - Fox Valley, 1874 Midway Rd, Menasha, WI, USA email: john.beaver@uwc.edu 4 Department of Physics and Astronomy, Appalachian State University, Boone, NC 28608, USA email: brileymm@appstate.edu Abstract. We present new CCD uvbyβ photometry of about 50 stars located in the central region of the open cluster NGC 6913. The individual stellar distances and color excesses of established cluster’s members are analyzed and new estimate of the cluster’s distance is provided. Keywords. Stellar clusters and associations, uvbyβ photometry, NGC 6913. 1. Introduction The young open cluster NGC 6913 (M 29) is located in a low-extinction area toward the Great Cygnus Rift. Despite several extensive studies, the distance estimates to the cluster are still controversial, differing by as much as a factor of two. Tifft (1958) sug- gested two groups at 1.6 and 2.1 kpc. Photoelectric uvbyβ photometry yielded 1.1 kpc, not in agreement with spectroscopically-based estimates (Crawford et al. 1977). More recently, utilizing Vilnius, BV and JHK photometry and spectra, Straizys et al. (2014) obtained 1.54 kpc. In order to re-evaluate the main cluster parameters, we provide new analysis of the existing uvbyβ data and supplement them with new CCD uvbyβ photom- etry of the central 15 × 15 arcmin region of NGC 6913. The uvbyβ photometric system (Str¨ omgren 1966, Crawford & Mander 1966) should in general be able to provide inde- pendent estimates of reddening, distance, metallicity and age, thus helping to constrain the existing disagreements. 2. Observations The data were obtained during three consecutive nights in May/June, 2008, on the 0.9 m WIYN (Wisconsin Indiana Yale National Optical Astronomy Observatory) telescope at Kitt Peak National Observatory (KPNO). The telescope was equipped with the S2KB CCD camera, which employs a 2048 × 2048, 21 μ-pixel detector for a field of view of 20.5 arcmin, and a set of KPNO uvbyβ filters.The reduction of the images followed standard procedures for bias subtraction, flat fielding, illumination and scattered light corrections 149 https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921316007055 Downloaded from https://www.cambridge.org/core. IP address: 52.90.119.67, on 28 Nov 2021 at 01:30:04, subject to the Cambridge Core terms of use, available at