The open cluster King~1 in the second quadrant


الملخص بالإنكليزية

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 $alpha_{2000}=00^{rm h}22^{rm m}$ and $delta_{2000}=+64degr23arcmin$. By parameterizing the stellar density with a King profile we have obtained a central density of $rho_{0}=6.5pm0.2$ star arcmin$^{-2}$ and a core radius of $r_{rm core}=1farcm9pm0farcm2$. 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 $2.8pm0.3$ Gyr, a distance modulus of $(m-M)_{rm o}=10.6pm0.1$ mag, and a reddening of $E(B-V)=0.80pm0.05$ 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 $leftlangle V_rrightrangle $=-53.1$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 $leftlangle [M/H]rightrangle$=+0.07$pm$0.08 dex. From spectral synthesis we have also estimated an $alpha$-elements abundance of $leftlangle [alpha/M]rightrangle$=-0.10$pm$0.08 dex.

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