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 $\hat{I}{\pm }_{2000}=00^{\mathrm{h}}22^{\mathrm{m}}$ and $δ_{2000}=+64\degr23\arcmin$. By parameterizing the stellar density with a King profile we have obtained a central density of $\ddot{I}{}_0=6.5\pm 0.2$ star arcmin${}^{-2}$ and a core radius of $r_{\rm core}=1\farcm9\pm0\farcm2$. By comparing the observed color-magnitude diagram of King~1 with those of similar open clusters and with different sets of isochrones, we have estimated an age of $2.8\pm 0.3$ Gyr, a distance modulus of $(m-M{)}_{\mathrm{o}}=10.6\pm 0.1$ mag, and a reddening of $E(B-V)=0.80\pm 0.05$ 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 $⟨V_r⟩$=-53.1$\pm$3.1 km s${}^{-1}$. From the strength of the infrared \mbox{Ca\,{\sc ii}} lines in red giants we have determined an average metallicity of $⟨[M/H]⟩$=+0.07$\pm$0.08 dex. From spectral synthesis we have also estimated an $\hat{I}\pm$-elements abundance of $⟨[\hat{I}\pm /M]⟩$=-0.10$\pm$0.08 dex.

14 pages, 18 figures, table 1 will be available at CDS, Accepted for publication at MNRAS