The open cluster King 1 in the second quadrant

Abstract

We analyse the poorly studied open cluster King 1 in the second Galactic quadrant. From wide-field photometry, we have studied the spatial distribution of this cluster. We determined that the centre of King 1 is located at α2000 = 00h22m and δ2000 = +64°23΄. By parameterizing the stellar density with a King profile, we have obtained a central density of ρ0 = 6.5 ± 0.2 star arcmin-2 and a core radius of rcore = 1.9 ± 0.2 arcmin. By comparing the observed colour-magnitude diagram of King 1 with those of similar open clusters and with different sets of isochrones, we have estimated an age of 2.8 ± 0.3 Gyr, a distance modulus of (m - M)o = 10.6 ± 0.1 mag and a reddening of E(B - V) = 0.80 ± 0.05 mag. To complete our analysis, we acquired medium resolution spectra for 189 stars in the area of King 1. From their derived radial velocities, we determined an average velocity = -53.1 ± 3.1 km s-1. From the strength of the infrared Ca II lines in red giants we have determined an average metallicity of <[M/H]> = +0.07 ± 0.08 dex. From spectral synthesis, we have also estimated an α-elements abundance of <[α/M]> = -0.10 ± 0.08 dex.